Took some time today to take a look at the AD-12. Attached a few pics below:
The screwdriver is pointing to the impact point on the plate. You can tell that I filed it a little to try to fix the clearance issue. It is hitting exactly the same without a key in it. My guess is that the key will hold it up just enough to allow clearance.
The armature plate itself does not visually appear warped
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