Unless the original paint has either pearl or metalflake, I doubt you could tell from a picture if it is factory paint.
Any good auto body guy can do a close inspection on the car and tell you if it has been repainted. There are ALWAYS some tell tale signs. Regardless of how reputable the dealer is, you need to get an independent specialist to give you an opinion.
I have not heard of widespread paint issues on that model. It is possible for any manufacturer to get a bad batch, and have several cars end up with inferior paint. Not the norm, but can happen. If a paint an body expert tells you it has not been repainted, then there is a chance it is just an inferior paint job from the factory.
I am a regular on bimmerforums (between my brother and I we have bought 59 bimmers over the years), so did a quick search over there and found this thread from last year about a 328 with paint chip issues:
https://www.bimmerforums.com/forum/s...ht=paint+chips
If you cannot see the pics on that thread, let me know, and I can post them here.