“There was an article in Surfer magazine within the last year that documented the corruption of the Federales down near Tijuana - the guys barely escaped with their lives after being robbed and beaten by the police. When they went to get help from the town police, they were robbed again.”
That is not an uncommon Mexico tale, it is not unusual at all to have multiple run ins with Mexican corruption during a single visit.
Each cop is a free agent, bribing one cop does not exempt you from the next one.