I've been FMQ with an old (1953) Singer 15-125. It's been wonderful until the last couple of days. I'm making a couple baby quilts. When I FMQ the top stitch looks OK, but the bottom side has big loops & looks a tangled mess. I've rethreaded both top & the bobbin (more than a couple of times) and I looked to see if the bobbin was dusty, but it was clean. The tension is at 4 and I've increased it to 6, but that didn't do any good either. One baby quilt is basted all together and I did a large meandering stipple throughout the body & the machine did just fine. The next day I wanted to do hooked feathers on the border & it does this loopy mess. Yesterday I worked for 2 - 3 hours trying to figure it out & couldn't...what am I doing wrong?