Lubricate Loaded Calipers? Brakes dragging intermittently

If it's locking where you can actually feel it, it's probably the pistons binding in the caliper bores.
Sounds like it anyway, from the having to stomp the pedal to get it to release.
In this case greasing things isn't going to help. (shouldn't have to grease anything anyway)
If it were my car doing that and not under a seller warrantee I'd pull the calipers apart and make sure the piston bores were nice and polished.
Talk to the dealer about it like you said.