Kani

I have a juki. It was doing the same thing. I checked tension and everything. Come to find out it was the presser foot.
I was about to throw it out. I noticed the little ring on the foot had marks where the needle had hit it. This is a midarm machine but I would check my foot to make sure the needle isn't hitting it.
Take the foot off. Check to see if the ring moves or if you have any place on the ring that looks as if the needle has hit it. The ring should not move. If it does you will have to fix it. Lock tight fixed mine.