Same thing happened to my car once a few years back... I'm sure it was never quite right after it was "repaired". Probably all psychological.
I'm not aware of an m330D.....the M135i is a specific model designation, like the m550D...they have started making half way houses between M powered and M-Sport cars...kinda like Audi that have A4 S-line, S4, and then RS4, the mXXX is similar to the "S4" middleground imo.
Curious to what makes it an M?
Is it like an M330d?


Round my way BMW use a repairer who doesn't have a particular good reputation. It was good when the father ran the business but since he retired its supposed to have gone downhill.
Just because they are "approved" doesn't necessarily mean they are the best. I'd do your own research into who is best
Gutted for you man.
Keep us informed of how it goes, fingers crossed for a decent outcome for you.