If the bobbin tension is too tight, that will definitely cause thread problems but I don't think it would show up on the top-it would be pulling the top thread down into the shirt. To test the bobbin-take out the thread, clean inside with a brush, and air-and slide a piece of business card under that tension 'plate' the thread goes under-see if there is gunk in there. I find lots of gunk when we've been using adhesive backing with a fastframe-it really clogs things after awhile. Put in the thread, but don't put it around the pigtail. Hold the end of the thread and see if the bobbin unwinds towards the floor. It should stay in place until you gently 'bob' the bobbin a little-then it should slowly unwind a little bit and stop again. If it unrolls all the way to the floor-its too loose. If it doesn't unwind a little bit-its too tight. The magnetic bobbins solve a lot of this adjustment problem-but you don't get as much thread per roll. Bobbin holders should be checked every time you replace a bobbin-because the bobbin thread itself can change 'density' (thickness of the thread) from one spool to the next-either from the factory machine that made it-or even humidity or dryness in your shop. Drier it gets-the thinner the thread gets. More humid-the thicker it gets. And the tension on the bobbin holder is set to the thread thickness-so every time you put in a new roll the thread itself can be different! The tech probably had it set perfect for his test, on the spot...and after you ran through that spool the next one could need a 'tweak' to work as good. We have 3 or 4 bobbin holders and load them all and test each one-then we can go that many bobbins without stopping. Once we use them up, we reload and retest each one. As for the sewout-if the bobbin is too tight-it pulls the top thread down. If the MT setting is too tight-then it pulls the bobbin up through the shirt. I've heard the new upgrade for the program will make the machine 'automatically' adjust density (MT) as it sews-this may cure your problem! I haven't tried it yet...but someone that has will probably jump in here. 5 oz. is definitely a lightweight material-when you consider that a teeshirt is 5.2 up to 6 oz. and I hate embroidering on those-try not to at all. There isn't much 'thickness' there to hold the embroidery without a lot of backing. Doing a top layer of solvy helps with holding the edge of the design or letter on materials like pique knit or tote bags.