Love my 335 and had no major issues! However, my CPO extended warranty kicked in and to me it's pretty useless since most of my issues are electronic and involve interior components (which aren't covered).
Computer throwing fault codes (reoccurring problem). BMW charging $150+ for it.
Air vent plastic just falling out (3 of them!!) lol. Each one is $150 as well for the whole piece that needs to be replaced.
Pixels disappearing on the head unit. I had same issue on my e36. 10 years and they still can't get it right. I've driven 3 cars between my 2 BMWs and haven't done any warranty work to any of them.