Well I took apart everything I could and found: no marks on the plate where the needle might be hitting but the bobbin race(?) seemed wobbly. I removed it, brushed off some lint, removed an unbelievable amount of lint from under the plate and replaced everything. While I had it off, i slowly turned the wheel to see if anything was rubbing or hitting, seemed fine. after I put the race back I did the same and all looked good. Tried sewing and all seems fine now.

I think "maybe" what happened: at some point the bobbin race became unseated, maybe from the original break(or a later one), maybe the thread WAS hung up and i didn't catch it. Combined with the extra lint from the minky it threw the machine off sync a bit. I'm good about cleaning out lint after sewing with fleece/flannel-anything linty- but maybe I underestimated the amount i would get from the minky.
I'm going to set the quilt aside for now and work on something else, just to see that all continues to go OK. I may finish this quilt with SID just in case my machine acts up again. I can always finish it on my old machine it it does. Thanks for all your suggestions. I hope what i found might help someone else. Back to sewing now!