Thanks for the suggestion. I should have mentioned this in the original problem description, but we have BPDU protection, Loop Detection, and all the ports forced to Edge except for inter-switch links.
I suspect you're right that it does have something to do with the wiring, a faulty switchport, or the AP(s) are themselves faulty in some way, Unfortunately we aren't getting much in the way of error messages from any of the components apart "Help, I'm dead".
We have in the past tried switching out the patch cables and the cable runs themselves have tested out good. Moving the AP moves the problem *sometimes* but not always, and the AP diagnostics don't yield much.
Perhaps, also, the title of the issue is misleading: I included Spanning Tree in the mix because the only thing that the switch complains about is having to put the port in block mode (but not as a function of the initial 3 second listening period for BPDU because the port is being forced to be an edge).