Just to confirm, the issue surfaced after replacing all the calipers (reread the OP)? If so, after replacing the ABS module (requires bleeding, probably done right), it continued. I'd suspect a bad caliper or component associated with only that wheel. The calipers are corner-specific, so swapping them is not an option (that would be too easy). Can you confirm that the driver side is working, or both are working at the same time? Jack both rear wheels and roll in D (chock front wheels, 2wd, obviously), at idle or slightly above, while very slowly adding pressure to the brake pedal. Note any chattering or instant locking, or anything else not normal. You may also try brake-locking on a dirt road. The problem may not be the locking wheel, if the other isn't getting enough friction, for whatever reason.