I'm an enthusiastic user of IT and some months ago I also began getting a similar problem. I use either Emdat InScribe or Word to work in and IT works fine there, but when I'm researching in Microsoft Edge and want to add an entry, this is what happens: The screen freezes for 10 seconds and anything I click/press on the keyboard won't work. After 10 seconds the Add Entry window pops up and any other action I've pressed beforehand will happen (and then adding the Entry works). So to avoid that delay, I always copy (control C) the phrase I want to enter, switch to eg InScribe and only then do Alt= to add that entry into IT. It's a workable get-around but might shed some light onto this problem.
(I tried this fix but the screen pops up that the computer is fine and doesn't need the fix.)