I don't know whether this has anything to do with it, it having been many years since I sewed on double knit. It was my understanding that polyester doubleknits respond best to a ballpoint needle. I'm probably not phrasing that correctly, but I had a terrible time sewing on my machine when I first started sewing on doubleknits, I haven't sewn on any knits in years! LOL!
Jeanette