What should I do if the upper thread tension is too loose and loops appear on the back of the fabric?
Increase the tension by turning the upper tension control dial to a higher number. If the upper thread was incorrectly threaded, the upper thread may appear too loose, so rethread the upper thread following the upper threading instructions. (Page 1)
From the official Brother XG4099-001 Computerized Sewing Machine manual, page 1
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