Drupal\commerce_order\Exception\OrderVersionMismatchException: Attempted to save order 125081 with version 8. Current version is 9. in /app/web/modules/contrib/commerce/modules/order/src/Entity/Order.php:682

I think this is caused by Commerce shipping, but not sure how to fix this unfortunately:

#6 /app/web/modules/contrib/commerce_shipping/src/Plugin/Commerce/CheckoutPane/ShippingInformation.php(349): Drupal\Core\Entity\EntityBase->save()

Perhaps we should have a try catch and reload the order when this happens. Are the order mismatch exceptions just logged? Or is an actual exception thrown?

The logs only show what I have shown here, however, I think that the root cause is here: #3282729: Always use checkout cart as main → .

What is happening is that if a user has multiple carts and logs in during the checkout process many times the order that they are checking out is the one that gets combined into the other cart. This shuffle is causing several bugs one of which is this exception.

Other issues it is causing:
The user is on a checkout on a cart that technically no longer exists so they cannot continue to review.
Google tag throws exceptions for trying to remove items from a cart that no longer exists.

I'm happy to work on the approach you discussed if you can point me where to start.

I am seeing this error.

Previous reports were closed as due to having custom codes and could not be resolved.
Current stack trace are not showing any custom code in the error.

I agree with the plausibility that when customer logs in during the check out process causing the error as I see a USER log entry for session opened just prior to this commerce_order error log

In checkout flow, there is an option to "Assign an anonymous order to a pre-existing user
If the email associated with the order matches an existing user account, the order will be assigned to that account."
Not sure if this has any relevance but it was something that was changed recently.

Drupal\commerce_order\Exception\OrderVersionMismatchException: Attempted to save order 4724 with version 6. Current version is 7. in /public_html/modules/contrib/commerce/modules/order/src/Entity/Order.php:703
Stack trace:
#0 /public_html/core/lib/Drupal/Core/Entity/EntityStorageBase.php(528): Drupal\commerce_order\Entity\Order->preSave()
#1 /public_html/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php(753): Drupal\Core\Entity\EntityStorageBase->doPreSave()
#2 /public_html/core/lib/Drupal/Core/Entity/EntityStorageBase.php(483): Drupal\Core\Entity\ContentEntityStorageBase->doPreSave()
#3 /public_html/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php(806): Drupal\Core\Entity\EntityStorageBase->save()
#4 /public_html/modules/contrib/commerce/modules/order/src/OrderStorage.php(169): Drupal\Core\Entity\Sql\SqlContentEntityStorage->save()
#5 /public_html/core/lib/Drupal/Core/Entity/EntityBase.php(354): Drupal\commerce_order\OrderStorage->save()
#6 /public_html/modules/contrib/commerce_shipping/src/Plugin/Commerce/CheckoutPane/ShippingInformation.php(349): Drupal\Core\Entity\EntityBase->save()
#7 /public_html/modules/contrib/commerce/modules/checkout/src/Plugin/Commerce/CheckoutFlow/CheckoutFlowWithPanesBase.php(546): Drupal\commerce_shipping\Plugin\Commerce\CheckoutPane\ShippingInformation->buildPaneForm()
#8 [internal function]: Drupal\commerce_checkout\Plugin\Commerce\CheckoutFlow\CheckoutFlowWithPanesBase->buildForm()
#9 /public_html/core/lib/Drupal/Core/Form/FormBuilder.php(536): call_user_func_array()
#10 /public_html/core/lib/Drupal/Core/Form/FormBuilder.php(375): Drupal\Core\Form\FormBuilder->retrieveForm()
#11 /public_html/core/lib/Drupal/Core/Form/FormBuilder.php(633): Drupal\Core\Form\FormBuilder->rebuildForm()
#12 /public_html/core/lib/Drupal/Core/Form/FormBuilder.php(326): Drupal\Core\Form\FormBuilder->processForm()
#13 /public_html/core/lib/Drupal/Core/Form/FormBuilder.php(224): Drupal\Core\Form\FormBuilder->buildForm()
#14 /public_html/modules/contrib/commerce/modules/checkout/src/Controller/CheckoutController.php(143): Drupal\Core\Form\FormBuilder->getForm()
#15 [internal function]: Drupal\commerce_checkout\Controller\CheckoutController->formPage()
#16 /public_html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array()
#17 /public_html/core/lib/Drupal/Core/Render/Renderer.php(638): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#18 /public_html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(121): Drupal\Core\Render\Renderer->executeInRenderContext()
#19 /public_html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext()
#20 /public_html/vendor/symfony/http-kernel/HttpKernel.php(181): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#21 /public_html/vendor/symfony/http-kernel/HttpKernel.php(76): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#22 /public_html/core/lib/Drupal/Core/StackMiddleware/Session.php(53): Symfony\Component\HttpKernel\HttpKernel->handle()
#23 /public_html/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#24 /public_html/core/lib/Drupal/Core/StackMiddleware/ContentLength.php(28): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#25 /public_html/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\ContentLength->handle()
#26 /public_html/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass()
#27 /public_html/modules/contrib/advban/src/AdvbanMiddleware.php(57): Drupal\page_cache\StackMiddleware\PageCache->handle()
#28 /public_html/core/modules/ban/src/BanMiddleware.php(50): Drupal\advban\AdvbanMiddleware->handle()
#29 /public_html/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\ban\BanMiddleware->handle()
#30 /public_html/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#31 /public_html/core/lib/Drupal/Core/StackMiddleware/AjaxPageState.php(36): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#32 /public_html/core/lib/Drupal/Core/StackMiddleware/StackedHttpKernel.php(51): Drupal\Core\StackMiddleware\AjaxPageState->handle()
#33 /public_html/core/lib/Drupal/Core/DrupalKernel.php(741): Drupal\Core\StackMiddleware\StackedHttpKernel->handle()
#34 /public_html/index.php(19): Drupal\Core\DrupalKernel->handle()
#35 {main}

I'm seeing this occasionally on a production system. In my case it seems related to ajax updates.

Affected URL: example.com/checkout/NNNNNN/order_information?_wrapper_format=drupal_ajax&ajax_form=1

[commerce_order] [error] <pre>Drupal\commerce_order\Exception\OrderVersionMismatchException: Attempted to save order NNNNNN with version 6. Current version is 7. in modules/contrib/commerce/modules/order/src/Entity/Order.php:719
Stack trace:
#0 core/lib/Drupal/Core/Entity/EntityStorageBase.php(528): Drupal\commerce_order\Entity\Order->preSave(Object(Drupal\commerce_order\OrderStorage))
#1 core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php(753): Drupal\Core\Entity\EntityStorageBase->doPreSave(Object(Drupal\commerce_order\Entity\Order))
#2 core/lib/Drupal/Core/Entity/EntityStorageBase.php(483): Drupal\Core\Entity\ContentEntityStorageBase->doPreSave(Object(Drupal\commerce_order\Entity\Order))
#3 core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php(806): Drupal\Core\Entity\EntityStorageBase->save(Object(Drupal\commerce_order\Entity\Order))
#4 modules/contrib/commerce/modules/order/src/OrderStorage.php(169): Drupal\Core\Entity\Sql\SqlContentEntityStorage->save(Object(Drupal\commerce_order\Entity\Order))
#5 core/lib/Drupal/Core/Entity/EntityBase.php(354): Drupal\commerce_order\OrderStorage->save(Object(Drupal\commerce_order\Entity\Order))
#6 modules/contrib/commerce_shipping/src/Plugin/Commerce/CheckoutPane/ShippingInformation.php(310): Drupal\Core\Entity\EntityBase->save()
#7 modules/custom/custom_retail_checkout/src/Plugin/Commerce/CheckoutPane/RetailShippingInformation.php(23): Drupal\commerce_shipping\Plugin\Commerce\CheckoutPane\ShippingInformation->buildPaneForm(Array, Object(Drupal\Core\Form\FormState), Array)
#8 modules/contrib/commerce/modules/checkout/src/Plugin/Commerce/CheckoutFlow/CheckoutFlowWithPanesBase.php(546): Drupal\custom_retail_checkout\Plugin\Commerce\CheckoutPane\RetailShippingInformation->buildPaneForm(Array, Object(Drupal\Core\Form\FormState), Array)
#9 [internal function]: Drupal\commerce_checkout\Plugin\Commerce\CheckoutFlow\CheckoutFlowWithPanesBase->buildForm(Array, Object(Drupal\Core\Form\FormState), 'order_informati...')
#10 core/lib/Drupal/Core/Form/FormBuilder.php(536): call_user_func_array(Array, Array)
#11 core/lib/Drupal/Core/Form/FormBuilder.php(375): Drupal\Core\Form\FormBuilder->retrieveForm('commerce_checko...', Object(Drupal\Core\Form\FormState))
#12 core/lib/Drupal/Core/Form/FormBuilder.php(633): Drupal\Core\Form\FormBuilder->rebuildForm('commerce_checko...', Object(Drupal\Core\Form\FormState), Array)
#13 core/lib/Drupal/Core/Form/FormBuilder.php(326): Drupal\Core\Form\FormBuilder->processForm('commerce_checko...', Array, Object(Drupal\Core\Form\FormState))
#14 core/lib/Drupal/Core/Form/FormBuilder.php(224): Drupal\Core\Form\FormBuilder->buildForm(Object(Drupal\commerce_checkout\Plugin\Commerce\CheckoutFlow\MultistepDefault), Object(Drupal\Core\Form\FormState))
#15 modules/contrib/commerce/modules/checkout/src/Controller/CheckoutController.php(143): Drupal\Core\Form\FormBuilder->getForm(Object(Drupal\commerce_checkout\Plugin\Commerce\CheckoutFlow\MultistepDefault), 'order_informati...')
#16 [internal function]: Drupal\commerce_checkout\Controller\CheckoutController->formPage(Object(Drupal\Core\Routing\RouteMatch))
#17 core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array)
[...]

I guess the ShippingInformation should use OrderStorage::loadForUpdate() when it is attempting to update shipments on the order.

Pushed a potential fix. This is intentionally violating coding standards for the sake of reviewability. Should the approach prove to be feasible, the blocks inside the new closures need to be indented properly before merging.