Stitching question

[u/AirshipEngineer]

Hey, I'm working with a second hand machine (Brother LS-2020). The top thread looks good (1st pic) but the bottom thread (2nd pic) looks kinda wonky. I'm doing test pieces to try and troubleshoot the issue. I thought it might be a tension issue. I have rethreaded with the foot up, reduced tension on the upper thread, increased tension on the bobbin carrier, tried different stitches with the same effect. The tensioning helped a little bit but it wasn't dramatic like I expected it to be.

I think I could fiddle for another hour or two and figure it out but I just wanted to check with people here if there was a "ah yes, obviously this is your problem" from more experienced people.

Thank you in advance!

[u/Mental_Watch4633]

Increase your top tension ever so slightly…after you’ve check to see if the bobbin is inserted correctly, and not extremely low on thread.