I can't evaluate your latch but I have seen many doors with the the old style "pin body striker" stick due to the tapered pin sticking in the reciever. Verify that the pin is hitting on the center of the whole and adjust accordingly. The real need though is for a little grease on the pin. A dry pin will stick even if hitting the hole on center.
Bosch Master, ASE Master, L1
33 years MB technician