The first thing I’d try is testing in a clean account. If the problem still exists, and you’ve done a clean reinstall of macOS, you’re left with hardware. Bad RAM could be a possibility, though that seems unlikely for a specific app. Flaky Bluetooth devices can also cause weird problems, so if you can unplug those or swap them for others, that’s worth testing.
I have exactly the same Mac, and while I’ve had quirks over the years that sometimes took me some time to troubleshoot, it sounds like you have something more serious.