After replacing Minor-Update related files, I got the following error after calling PHP Fatal error: Interface 'Commerce Guys\Addressing\Model\Address Format Interface' not found in [...]/modules/address/src/Entity/Address Format on line 21 "composer drupal-update" didn't resolve the issue for me.
Sounds like you replaced your vendor directory with the one shipped with core.
I ran into a very similar issue after updating to 8.1. I did not mean to imply this was the proper fix for the issue - not by any stretch.A likely cause is the memory limit in default php installations (usually 8 MB). If the page just hangs loading during some time (like 30 seconds) doing a specific action, and then it results in a blank page or HTTP 500 error, the problem is a timeout connecting to some server.This may be the database server, or if it happens doing a specific action, the mail server (if you have configured email settings).What I need is a summary of all date issues that are in play.I'm now getting lost and not sure at which patch(es) I should take a look.