Since last Windows Update "task host window is stopping background tasks windows 10" on 4 machines

Yep, I have exactly the same issue.

For me it is since the two updates - KB5016616 and KB5012170.

So I don't know if this narrows the culprits down from the 3 updates you mention.

Hopefully this will be sorted soon. It's irritating.

Very unlikely for me.

And many others have now reported the same issue when updating to KB5016616 and KB5012170 ... it has now been reported to Microsoft

The KB5016616 update updated the Servicing Stack to version 10.0.19041.1852. The Servicing Stack has to do with Windows Updates, so perhaps this is root of the issue. I read that once Servicing Stack updates are performed they cannot be removed. See here:

https://docs.microsoft.com/en-us/windows/deployment/update/servicing-stack-updates

So even if you uninstall KB5016616, the issue may persist until Microsoft releases a new update that includes a fixed new version of the Servicing Stack.

I'm also having this issue and am waiting for Microsoft to fix it.

...and all of the so-called "solutions" don't address the underlying problem of a hung/leftover instance of task host window due to a bug in coding/logic in how windows services (mainly windows update) use the aforementioned process and how the aforementioned process regulates/terminates itself once it should detect that it has nothing to host. Perhaps there is some disconnect between different coding teams. The registry hack sweeps the issue under the rug and simply forces a shutdown after a set amount of time. Not a good idea to prevent data corruption over the long term. This is something that should be fixed/re-coded robustly by all the different teams within the OS group that work on common interop standards for processes that host other activities and pushed out next patch Tuesday before the mess compounds.

I have the exact same problem. None of the fixes listed here fix the problem. I have noticed that if I reboot my system early after startup without letting my system idle, the problem does not occur. I also noticed that windows update likes to do 2 rounds of background work/checking for updates - once right after startup and another batch of work later during idle time. It's after this second batch of activity that some background task hangs or doesn't get terminated and persists until it's time to shutdown.

Update: I have also reported this on feedback hub: https://aka.ms/AAhrgj3