The admin on a Xenforo forum I use suggested I post on here, got users having similar problems:
Gboard and SwiftKey having problems just on Xenforo forums. For me it commonly happens when a suggestion on the app comes up above the keyboard but it won't replace the gibberish on screen no matter how many times you tap it.
Okay, glad to see it isn't just me. I've been running into this for a while on my own phone (Android 7, GBoard) but haven't really heard from many users about it (though a lot of my users are on PCs or Apple devices). Thread watched.