Juki 8300N. I purchased this machine about a week ago and am pulling my hair out!! It works fine

Question

I purchased this machine about a week ago and am pulling my hair out!! It works fine for a little while, and then when it comes over a seam (denim OR light cotton) or for just no reason at all, the thread gets cut or unthreaded, etc, it's no longer in the eye of the needle. Help would be SO appreciated, thanks!!