I have a consistent problem with one brand of thread breaking in my machine, which is the same make and model as TechShop has. but some people have been able to run this same thread on the TechShop machine with no problems. the brand happens to be Coats & Clark, but I really don't have any idea what's causing the problem.
when I switch to a different brand and leave everything else the same, it embroiders fine. when I finally gave up on this thread, I moved every spool of it into my "non-embroidery thread" drawer. it works fine on the regular sewing machine. months later I accidentally grabbed a spool of this brand - I missed it when I was culling my embroidery supplies of this pariah. sure enough it started breaking and I noticed it was That Brand.
recently, I was fresh out of good peach color embroidery thread. but I had it in this other brand. to save myself a trip, I tried it. I even slowed the machine down to 400 stitches per minute. hey, it didn't break. but it was terribly loopy, looked like I was a beginner terrycloth maker. unusable.
I even took a closeup image to see if I could see any reason how these two threads are different and if there might be some suggestion why it breaks. totally obvious what the problem is, right? yeah, I can't see a difference either except for color.
I only post this story to let embroidery newcomers know that at least in my experience, some problems can remain unexplainable even with a fair amount of research and you might want to just keep changing things until you get something to work. if you're having problems, check out my Embroidery Problem Checklist to see what else you might change.
I usually use Sulky or Madeira thread. I've had very bad luck with the cheap serger thread, which I tried to use just for preliminary design layout. these are the big cheap spools that work great in a serger. they break every couple hundred stitches in my embroidery machine.
if you know threads or know anyone in that business who has ideas why this might happen, I'd be curious to hear.