I was having the intermitten eyelash problem on the back and couldn't figure out why. I started doing research and found out that when you thread your machine, you need to be sure the presser foot is UP so the thread can get properly seated between the discs. I have made sure ever since and have not had the problem again.
Also, when removing the bad quilting, I also, as stated above, snipped and pulled out the bottom thread which left the top thread easy to remove...and there were yards and yards of it.