SharePoint 2016 – Office Online – Why are we passing a null request when creating a response?

Yesterday I was working with one of my SharePoint 2016 clients and I hit a bit of a weird issue. There is one user who when he opened multiple documents in Office Online (e.g. OneNote Online, Excel Online, Word Online) and keeps these documents open for a while  he will find Office Online locking him out.

This then results in errors like the one shown below

Something went wrong and we couldn’t load this content. Refreshing the browser might fix the problem.

Well, refreshing the browser does not help. Waiting for a while does help as the files seems to be unlocked after about 1 hour. So I told the user to go for a run around and then all is fixed, but that didn’t work in the long run

Time to look at the ULS logs for Office Online then.

This is where I found the critical error:

Why are we passing a null request when creating a response?

With a bit more searching around I also got some more unexpected error message:

Wopi,CheckFolder,WACSERVER ConfigError [error:The SharePoint site appears to have its UPA in an improper sync state. Please contact the SharePoint administrator. The SharePoint site’s WOPI handler has determined that the user permissions for this file/folder do not match the user permissions when wopiframe.aspx was loaded

Then I found an article describing the same problem in SharePoint 2013 telling me to  recreate the user profile.

Having tried recreating the user profile I found that the problem still existed. It looks like there is an issue with this user’s AD /user profile details. If you have seen this problem before then please let me know.