Okay, so I’ve just been given a Brother GS2500 sewing machine, and I’m sure I’ve threaded it all correctly (checked the manual and all) and whenever I sew, no matter what speed, what setting and no matter what the tension is on, the thread underneath bubbles and is super loose. It’s basically a bird’s nest of thread underneath! At first I thought it must just be the tension setting being too low, but even if I crank it right up to the highest setting (I’ve tried all of them!) it still happens! I have something super important to sew, and I was given this machine because mine is away for servicing and I have no idea what’s up with it! The fabric I need to sew is super delicate too, so I really don’t want to be unpicking every 5 seconds and making unnecessary holes in the fabric because it would fray so fast. Any help ASAP would be greatly appreciated!