Assertion: bobbin's thread | /r/CapableOf | lock up below the needle plate
Facets:
Source sentences:
text: Important note before making adjustments: If you are suddenly experiencing a lot of top thread locking up below the needle plate then this is likely to be a top thread tension issue where there is contamination in the upper tension unit or a damaged bobbin case (sometimes caused by a jam or needle breakage) or the bobbin case has been inserted incorrectly.