Hi Rolf,
Using a #3 blade, tension isn't an issue at all, I have that figured out and have the correct "ping" of the blade. The saw is vibrating like crazy and even the blade vibrates so much side to side that I am unable to start a cut on a line precisely. I shot 2 videos of this and sent them to BM for review.
The vibration is also so bad that as I mentioned, it's literally vibrating the set screw out that adjusts the forward/backward pitch of the blade and when that happens the puzzle pieces will not slide. I realize a dab of medium strength Loctite will help with that but I am not going to do anything without instruction from BM. Unless the vibration issue is resolved, there's no reason to worry about the set screw at this point.
At this point the saw is completely unusable and I'm approaching 2 months since I placed my order on June 11th.