I have a brother 6000 that i bought from walmart about 8 yrs. Ago and has been a good extra machine but has a problem right now and i can't seem to figure it out. It bunches up on the bottom. Have cleaned it, changed threads, needle, tension don't know what to do next......gave up and back to my babylock again.....any suggestions? I love the little light weight machine. Have done lots of quilting on it even queen size quilts.