just had an issue with my V2 hotend (Support case is open): The hotend was leaking on the top where it's screwed to the little metal plate. So I replaced it (300h printing time with my M300) with the one that was in the package luckily and everything is fine again. Funny side-effect: I always had dark spots and marks after a certain printing time right from the beginning with the M300. With the hotend- replacement it's gone... so far...
I'm not so sure... I guess the hotend could be improved...
Every print the nozzle hits the plate a little to set distance... I guess this can lead to weak spots as the one where the plate is screwed to the hotend right?
Zortrax is there a hotend v3 in the labs?
PS: Support is helping very fast btw!