Quickbooks 21, up to date. Windows 10. This is on the server. 

Scenario: Only the Admin is logged in to the Quickbooks file, which is in Single User mode. I click File and choose "Switch to Single User Mode". I get an error that says "You cannot switch to Single User mode because someone else has just started using the file in Multi User Mode." I clear the prompt and Quickbooks relaunches into Mutli User Mode. I get an error says "Only one user may use bank feeds at the same time. Another user (something something...)" I clear this message and Quickbooks seems to freeze. Maybe it'll load, I don't know, I run out of patience about 10 minutes into waiting and end task and relaunch.

This problem existed back when we were on QB 18. At that time, it was a crapshoot whether or not I'd be able to reopen the file at all. That part of the problem was solved by upgrading to 21, but the former problem persists. 

I have done data verify and data rebuild. Doing this fixes some problems (unspecified) but says that it couldn't fix everything. It then suggests that I contact the Intuit Hold Music Player Service for help. 

I know that the next suggestion will be to download QB 22, but I prefer to wait until a new product is in the channel for about 6 months before doing a major version upgrade. Plus, this problem has survived upgrading from 18 to 21.