You say the problem happens more often after you have lowered your feed dogs and then raise them again when you do free-motion quilting. I would not lower the feed dogs any more. You can free motion quilt by setting your stitch length and width to Zero..so they remain Up but no longer move. This is what I do after reading this tip from Leah Day's website for learning free motion quilting. I also have the same machine as you.
I wish your machine a speedy recovery!