I am having bottom tension issues on a couple of Juki DLN 9010A-SH...one brand new machine and another that is only about 8 months used. The issue is bad tension on the underside of the fabric only when the machine is doing a reverse stitch using either the reverse lever or the reverse button. Tension is great when sewing forward.
Things that I have checked adjusted, re-adjusted, tweaked, changed you name it:
Machine head properly threaded
Brand new needle size 18, installed correctly
Bobbin tension
Burs on hook
Needle & hook timing
Check spring tension
Presser foot tension
Feed dog height and positioning
Put new feed dog and needle plate on
Tried different presser feet
Measured forward and reverse stitch length which both came out equal
Am I missing something or is there a problem much deeper in the machine?