bonnieba

Machine noise from bobbin area making me crazy. Here are the facts:

Juki F400 domestic sit down

1- machine sews fine. Noise doesn’t affect quality of stitches but it is a rubbing/scraping noise that is worrisome
2- when all thread is out of machine it purrs beautifully
3- loaded with thread and fabric, makes pretty loud noise after about a minute of warmup
4- remove bobbin thread and fabric and just run it with top thread inserted, it will make the noise.
5- this is drop-in bobbin case and I suspect, but don’t know for sure, that thread is rubbing over bobbin case as it revolves around hook. Is this making the noise ? Really hard to tell,

Does anyone one have any inkling of what this could be? I am afraid that I have to wait until this pandemic is over to bring it for repair, thank you so much for any ideas!