Lock keep sticking.

I know that there are a lot of threads about this but none quite like mine. So on my 01 325xi my door was not locking by turning the key. I replaced the key lock the first time and it broke into pieces after being used for 6 months. I recently ordered a new lock and master key from bmw ( oem parts) and when i installed it, it worked... for a couple of turns then it started to stick and eventually have the key stuck in the door. I can lock and unlock the car from the key fob but can not manually unlock it with the key. Any suggestions on whats my problem ??. Need answers ASAP

Lock keep sticking.