Stich tension (by 2 users)

SE-270D worked fine at first. Sewed three tops. Tried embroidering - first three colors went ok but the fourth one created 1" loops of top thread hanging below and eventually jamming the machine. No adjustment of top thread tension, material, stabilizer, type of fabric or thread has helped. Now even back to regular sewing a zigzag stitch looks ok on top but bottom looks like top thread pulled through both sides of the stitch and a narrow zigzag of bobbin thread down the middle. Have tried all tension settings and making sure shuttle is very clean. Really NOT liking this machine.