Thank you for any ideas, I am not sure what to try next.
I was having a "rats nest" on the bottom side, but I've gone through all of the timing points in the Navy manual, and now I have the topside looking great, and the bottom side with the bobbin thread just running in a straight line and the spool thread pulled up against it.
I have increased the tension to a ridiculous amount and it didn't make any difference. The tension assembly is not disengaging, I adjusted it temporarily so that it doesn't open the tension discs even when the presser feet are raised. The tensions discs are not bad either, there is definitely no lack of tension on the spool thread.
I read in the Navy manual that this problem happens when the eccentric is out of timing, and when the bobbin case opener isn't adjusted correctly and doing its job. I've adjusted both.
Any ideas are appreciated! Thank you.