Cannot update the order weight using complex form widget

This is a duplicate of 🐛 IEF complex widget: Re-ordering / weight sometimes not updated Needs work . Both issues have patches with widely different solutions. We need to figure out which one to implement (if any). Both patches need tests. The less desirable solution's issue needs to be closed after granting credit to all contributors in the other issue.

For what it's worth, I think that this is the patch we use on my sites, but I'll have to verify that sometime when I'm at work.

Also, if this doesn't cause regressions, then it may indicate that this code is unnecessary. And I'd rather remove unnecessary code than add the new code that's in the other issue's patch.

Just FYI, I tried to reproduce the issue so that I could write a test, but I couldn't make it happen. And yet I know that we've had this problem at work. I have actually seen this problem in action. So if anyone can provide us with reliable steps to reproduce, then I'll volunteer to take care of writing a test.

@dcam: Sounds very reasonable. Rock on!

This needs a patch for the 3.x branch.

The MR should contain the same change as https://www.drupal.org/project/inline_entity_form/issues/3033241#comment... 🐛 Cannot update the order weight using complex form widget Needs work