Hi,
I have 2 computers where I use 2 (different of course) email accounts in each one, converted to Microsoft account and made both admin. In brief, 1st computer has email accounts A and B, both converted to MS account and both made admin. 2nd computer, idem.
When the mentioned anomaly happens, it persists until I log off the session and back on. Curiously, if I don't log off the session but switch to another user/account, the Windows Update window works correctly, and I'm able to see the updates available.
The anomaly happens eventually (as already mentioned) and it doesn't matter neither which computer nor which MS account.
My computers are not in a domain.
Although I have used Windows Update Troubleshooter (for other reasons), I don't think the problem is "within its reach"; I guess it's related to some weird interaction between programmed objects.