The clamp is flattening a bracket that should already sit down

I'm making a trial nest for an FR10 handling drilled aluminium angles. Three sample brackets sit nicely, two rock between the rear face and one bottom pad. The suggestion is a bigger clamp. That would certainly stop the rocking while held... it might also bend the part. I want to map the intended locating contacts before we make more bits. Where would you start checking for a conflict?