Please try restarting the Mac in safe mode and check the performance of the application.
If the application works in safe mode. Try restarting and check if that works in normal mode.
Also if you have any third party extensions installed on any browser, try removing them and restart and check if that helps.
That worked like a charm (also fixed a few other 'glitchy' little things, too!).
Of course, all that harkens back to the old days of restarting the machine with "extensions off", followed by reloading individual extensions one-by-one-by-one — restarting the machine each time with every single extension reload — until a culprit (or culprits) was found. Things work so consistently well with Macs (and associated software) these days that I hadn't even THOUGHT of going the 'safe mode' route!
I appreciate the response, Nikhil! Thanks!
Glad to know that everything worked fine.