A couple of prints after leveling the bed (<10), I noticed some weird sound, and saw the nozzle scratching the build-plate. What is really weird, is that I noticed (My printer is in quite a dark edge, so the build plate isn't really illuminated), that there were some scratches from a print before, but it worked fine with the prints in between. So my question is, how that might have happened, could it be also software issues (Maybe some mistakes converting to gcode?), or is this propably purely a mechanical issue? Furthermore, I'd like to ask whether this may cause any problems, e.g. massively reducing print quality, or weakening the grip of the prints.
I'm using the Tevo Michelangelo 3D, with manual leveling (it drives to the positions, but one has to tighten/loose the screws). Note that I might have overtightened the screws in the beginning. Another thing I noticed is that the screws on one side tend to be more loose than the other ones.