After more digging into this issue:
I took the test flow, and reconstructed the whole process from starting up IE to closing the windows I was interested in. Running the complete process test script, everything works fine.
Embedding the appropriate code back into the existing framework, for the window closures, the issue is still there.
I am quite sure the last code part is solid and good, but I need to figure out what is going on in this framework from starting up IE to get the browser windows opened that causes the IE crash after closing the last opened browser window in the cleanup process.
It was great to see the toggle for the Legacy IE process under Web testing !
That came in useful for some debugging.
That's it for now.
This is a strange issue.
