Kinda sounds like it's not picking up the bobbin thread. Did this once myself on a quilt, stitched a whole row with an empty bobbin. If the bobbin is full, possibly the bobbin carrier isn't seated fully. No seeum and thulle are both a pain to sew but this seems to be more of a thread injector problem.
Most of us end up poorer here but richer for being here. Olddog, Fulltime hammocker, 365 nights a year.