My for lock shuts fine for a few days then it needs oiling , only a quick squirt, if I don't squirt it then it bounces open and isn't shut properly unless you shut it be be gently , I have spent hours adjusting the striker plate and no matter where I position it then it is the same , thiis a real pain in the neck , is the lock knackered????

 

I have the same issue with the front passenger side door of my car, a gentle firm closing and it will latch any normal or harder closing and it does not latch I have tried various lubes.