And please don't share with the repair person that you used canned air on your sewing machine . . .
I agree with Shirley - it probably is your timing off.
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Ditto! Canned air just pushes lint balls into tighter places.
Never, ever blow in to or use canned air to clean lint out of your machine.
My first sewing machine did exactly that and it was the timing. I went nuts trying to figure it out and tried everything. I brought it in to the shop they ran it two seconds and said timing. It was a cheap machine It so cost me less to buy a new one then to fix it.