"error":"Client could not be found." for oauth2_server module

Hello,

I am using oauth2_server module in Drupal 8 site which is Provider and I have D7 sites which are Relying parties. I have set up a flow where, user clicks on login in D7 Relying site, gets redirected to D8 Provider when the user enters the right credentials he/she will login to the D8 Provider and redirect the user to the D7 Relying site. The flow is working well but some times after the user enters the credentials on D8 Provider, the site errors out with a blank white page with this error --> {"error":"Client could not be found."}
I have also pasted below the log from the Drupal error log message. Please let me know if some else is facing the issue and how to fix it.

Deprecated function: Function mcrypt_create_iv() is deprecated in OAuth2\ResponseType\AuthorizationCode->generateAuthorizationCode() (line 89 of /var/www/www.website.com/vendor/bshaffer/oauth2-server-php/src/OAuth2/ResponseTyp...)

#0 /var/www/www.website.com/web/core/includes/bootstrap.inc(582): _drupal_error_handler_real(8192, 'Function mcrypt...', '/var/www/www.we...', 89, Array)

#1 /var/www/www.website.com/vendor/bshaffer/oauth2-server-php/src/OAuth2/ResponseTyp...(89): _drupal_error_handler(8192, 'Function mcrypt...', '/var/www/www.we...', 89, Array)

#2 /var/www/www.website.com/vendor/bshaffer/oauth2-server-php/src/OAuth2/OpenID/Resp...(55): OAuth2\ResponseType\AuthorizationCode->generateAuthorizationCode()

#3 /var/www/www.website.com/vendor/bshaffer/oauth2-server-php/src/OAuth2/OpenID/Resp...(26): OAuth2\OpenID\ResponseType\AuthorizationCode->createAuthorizationCode('azcitrb', '5087', 'https://az-citr...', 'openid email pr...', 'eyJ0eXAiOiJKV1Q...')

#4 /var/www/www.website.com/vendor/bshaffer/oauth2-server-php/src/OAuth2/Controller/...(90): OAuth2\OpenID\ResponseType\AuthorizationCode->getAuthorizeResponse(Array, '5087')

#5 /var/www/www.website.com/vendor/bshaffer/oauth2-server-php/src/OAuth2/Server.php(303): OAuth2\Controller\AuthorizeController->handleAuthorizeRequest(Object(OAuth2\HttpFoundationBridge\Request), Object(OAuth2\HttpFoundationBridge\Response), true, '5087')

#6 /var/www/www.website.com/web/modules/contrib/oauth2_server/src/Controller/OAuth2C...(90): OAuth2\Server->handleAuthorizeRequest(Object(OAuth2\HttpFoundationBridge\Request), Object(OAuth2\HttpFoundationBridge\Response), true, '5087')

#7 [internal function]: Drupal\oauth2_server\Controller\OAuth2Controller->authorize(Object(Drupal\Core\Routing\RouteMatch), Object(Symfony\Component\HttpFoundation\Request))

#8 /var/www/www.website.com/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingC...(123): call_user_func_array(Array, Array)

#9 /var/www/www.website.com/web/core/lib/Drupal/Core/Render/Renderer.php(582): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()

#10 /var/www/www.website.com/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingC...(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))

#11 /var/www/www.website.com/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingC...(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)

#12 /var/www/www.website.com/vendor/symfony/http-kernel/HttpKernel.php(151): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()

#13 /var/www/www.website.com/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)

#14 /var/www/www.website.com/web/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)

#15 /var/www/www.website.com/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle...(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)

#16 /var/www/www.website.com/web/core/modules/page_cache/src/StackMiddleware/PageCach...(99): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)

#17 /var/www/www.website.com/web/core/modules/page_cache/src/StackMiddleware/PageCach...(78): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true)

#18 /var/www/www.website.com/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMid...(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)

#19 /var/www/www.website.com/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMidd...(50): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)

#20 /var/www/www.website.com/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)

#21 /var/www/www.website.com/web/core/lib/Drupal/Core/DrupalKernel.php(664): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)

#22 /var/www/www.website.com/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))

#23 {main}.