that or its coincidence, classic shell only affects its own registry settings, so its unlikely. However maybe something 'refreshes' when the something new is installed. Ive actually had this issue myself, and downloading an update for another piece of software fixed the issue (however it came back a few days later)
If it does come back, try a system shutdown to see if that fixes it, and report back if possible
It could be related to classic shell, because it does throw a start button in-front of everything windows 10 could be giving the button itself focus (the software that I updated last time also created a button on the titlebar of every window)