Machine is a Juki DNU 1541.

Problem solved.
I also posted this to a group on FaceBook, and came up with several suggestions:
Replace needle (I do this this frequently)
Loosen tension (I did this)
Lengthen stitch ( I also did this)

Problem still existed, but only with that particular thread. I replaced the whole spool, voila, problem solved. Turns out it was an old spool and the thread was sticking together.

What brand of thread was it? It seems lately I myself and reading a few other problems that new to us, spools of thread, are old and causing issues. Is this a supplier problem of over ordering and sitting on the shelf too long?

I used to have that problem in that the suppliers would store the thread in a hot environment in the summer and if the thread had any wax as lubricant it would melt and stick the thread together.

Thanks for sharing the solution with us @Clay Hurtubise. This is really good to know, because some of our spools are ancient... best to replace them with a fresh spool before starting really important projects.

It was a spool that I inherited from another trimmer, so I wouldn't blame the mfg (though I'll check if you want), but rather storage conditions. I'm guessing the thread is 5-7 years old, and when I first inspected it, it seemed fine. As I took more off, I could feel it sticking together.

@Clay Hurtubise no you don’t have to check. Being that old anyways it makes sense.

I discovered that also. Thread does have a shelf life. If you have boxed pre wound bobbins check them as well.