Hey all! Checked 6he forums but didn't see one quite like this, so hoping someone can advise.

Recently picked up an 01 Tahoe - pretty decent shape overall, all things considered - but with a few small annoyances. This is one of them:

Door locks. They lock and unlock as expected from vehicle movement (lock at 15mph, unlock when parked and remove the key). So the locks themselves work. But they won't lock or unlock from either interior switch.

I tried replacing the switch set on the driver's side. No joy.
Can't test with remote, as the fob I got with it was broken - and of course can't program the new fob if the switch isn't working.
I've checked fuses (at least the ones that I can tell are related), all good.
Checked out a relay tester and will test the relays - although I think that might be a long shot if they actuators are working as expected.

Additional (maybe related?) issue - power mirrors do not work.

Folks at my parts store think it could possibly be a body control unit getting flaky - but not gonna chuck that money at it as a diagnostic.

Any words of advice/things to check?

Thanks in advance...