Sometimes the hardest part of fixing any problem is troubleshooting. If there's one piece of advice that I could offer that is crucial to any troubleshooting task, it would be to always test only one thing at a time. If you test more than one thing, you won't know which "thing" fixed the issue.
Tension problems are one of the most frustrating issues for sewing and machine embroidery. Somehow, it just starts going berserk. Maybe the bobbin threads are coming up to the top or the needle continues to break. Your first instinct is to clip the thread and rip it from your machine. Stop and take a deep breath.
Take a look at things before you start pulling the thread out. Leaving the thread in its position when the tension starts going off might give you a clue of what's going wrong.
Generally speaking, if you have a problem on the underside of your fabric, there’s something going on with the upper portion of your machine, and vice versa. Look at the thread path and make sure that the thread itself hasn't gotten hung up on anything.
Nine times out of ten, thread nesting or "thread throw up" (a major mess of thread on the underside of fabric) occurs due to how the machine is threaded. Usually, the thread doesn't get seated properly in the take-up lever (the silver bar that goes up and down as you sew) and you immediately get a thread nest when you start to sew.
If everything looks clear, there may be fibers caught in your tension assembly. One way to clean it is by flossing your machine.
Thread problems on the top side of your fabric may indicate an issue in the bottom section of your machine, the bobbin area. Double-check your bobbin case to make sure you have the correct sized bobbin in there. A lot of us have different machines and they take different sized bobbins and it's really easy to pick up the wrong bobbin and put it in the wrong machine. You may want to mark your bobbins with a magic marker if you have different machines and different sized bobbins to avoid mishaps in the future.
You can get more tips for avoiding thread nests and broken needles here.
Have a day blessed with perfect stitches and GlitterFlex!!