"A critical error has occurred"

I did some searches through Google to see if someone somewhere on any forum has encountered this issue that I have, but I turned up with nothing, so I'm posting it here!

I am using an HP laptop with Windows 10, for reference. It's relatively new; I got it around October or November last year.

Basically, at the end of some games (and I believe they were all ranked games), my screen freezes on the end-game screen (usually it freezes on defeat screens, not victory ones), and I cannot switch to any program or another screen at all. I can press ALT+TAB and then see what else is open, but I cannot actually switch to them. And, in one of those windows, is the same message as here: https://m.imgur.com/a/lVV1E (this image was used in a PBE thread a few months ago).

Since I cannot switch screens --even if I CTRL ALT DELETE and select Task Manager, I am still taken right back to the defeat screen; that defeat screen seems to override everything but signing out of my account and/or shutting down my laptop -- I can't create or send a crash dump file from that window, so I feel rather helpless.

I can still move my mouse around and even press ALT TAB to close *other * windows, e.g. chrome or spotify (which I keep minimized and dormant during games anyway) but doing so never helps at all ;w; and again, I can't get rid of the screen, save for just hitting CTRL ALT DELETE and clicking "Sign Out" or "Shut Down." This problem has been happening randomly the past week, and hasn't happened before this week.

Anyone have any ideas as to what the problem is or as to what a solution could be? Is it the new anti cheat stuff, is it my antivirus..?

(is it my bad gameplay oof)