Apple wireless keyboard going nuts after upgrade to newer Mac mini

[AVR2]

I've just upgraded from an early-2009 mini to a late 2012 (I needed the built-in FireWire) and now my Apple A1314 Bluetooth keyboard, which I've had for years and which previously worked fine, has gone nuts.

It works normally for a while, but then randomly seems to go to sleep, even though it still says "Connected".

Sometimes it'll randomly disconnect.

Other times you'll start typing and there'll be a flood of repeat keypresses, e.g. you press backspace/delete once, and it decides to keep going and delete the entire sentence.

Things I have tried: removing/re-pairing, zapping the PRAM, doing a factory reset on the keyboard.

My Bluetooth mouse works fine. This is all happening under 10.15.7.

Any strategies I've missed?

 

[AVR2]

Is there any way to make the Mac completely forget it ever saw the keyboard before? Even though I've done the factory reset procedure twice, whenever I go to re-pair, the Mac always shows the keyboard by the name I set years ago when I originally set it up on my older mini, whose account I migrated across to the new one.

EDIT - I deleted the two Bluetooth .plist files and restarted, but even then it still immediately recognised the keyboard by the name I set years ago, not by its factory name.

 

[AVR2]

Well, it's a year and a half later, and I've finally fixed the problem. It was all down to the poor RF shielding around the wireless module on some (but apparently not all) 2012 Mac minis, which caused Bluetooth interference issues - and hence greatly reduced reliable range - if you had any USB3 devices plugged in.

Adding cheap clip-on ferrite cores to the USB3 cables has made the issue go away.

Quite why I didn't discover this at the time I don't know; all my Googling pointed to Catalina issues rather than a fundamental hardware issue. Hopefully this might help someone else.