Probably 20 hrs into trying to fix this.
Have the Engineer manual and general user guide, and parts book. Did all the suggested adjustments, plus more:
Needle bar/ shuttle hook timing
Shuttle spring alignment
New knives - adjusted and adjusted over and over again according to manual and beyond. That's height, swing, clearances and counter/moving relationship
New needle(s)
New needle plate
Different bobbins, including pre-wound, and new case
Different thread size and types
Trying to use DP5 18-21 size needles, 69 bonded nylon thread plus 46 to just do something else
Sewing webbing and Cordura