help with bobbin thread tension, Janome

[MissFoodie]

just got brand new machine (Janome 7025, same bobbin holder as 525S and DM200), keeps tangling, esp in reverse; from what I can ascertain is my bobbin thread tension, so took out holder and loosened it, works fine for a bit then starts again......could it be anything else????

There's a screw or 2 you can play with, I think.

yes, the one in the bobbin holder, loosened it....does it again....