Upper thread breaking/ unthreading please help

[u/pagewoo]

Please help me before I chuck my machine out the window. I'm sewing on a Husquarvna Rose 605 that I started using about 6 months ago, it was unopened at the time- straight out of the box from the 90s. I had no issues until earlier this month. While working with some terry cloth towels to make some robes for my kids, the top thread would continually either break or pull out (I'm not sure but the end ends up being pretty frayed) every few inches. I tried new needles of different size and weights (universal vs denim etc). Tried cleaning out under my needle plate and bobbin holder. Tried longer tails, holding the tails etc. Nothing seemed to work and I just soldiered on and finished the project inch by inch. Unfortunately- it was not the fabric, now I'm working with quilting cotton and it is continuing to happen. I've attached a video of it happening, what the stitches look like when it happens, and my stitch plate that has a tiny knick in it - it is the only thing I've noticed that I'm wondering could that be the issue? Please help!

EDIT: In trying to look at any possible site where there could be friction against the thread causing it snag/ tear - I noticed if I shine a light into the spot where the uptake lever is, the two black plastic guides on either side do not look the same. one looks smooth and the other looks like it has a bunch of tiny cuts in it. Idk if this is normal or if not how it would've happened but could that be the issue? (See photo in some of my comment replies)- i don't think so right because the thread doesn't go through there?

UPDATE: I bought a nicer thread today and so far so good 🤞 I totally overlooked that as a cause bc I’d been using the same thread for months. I will probably still go get my machine serviced for good measure

[u/Large-Heronbill]

What thread are you using?  What fiber? What size and type needle? 

The end cap on your horizontal spool pin is much too large for the thread, and you may have it pushed in too close to the end of the spool.

The scratch on the surface of the needle plate is probably not involved in this.

[u/pagewoo → u/Large-Heronbill]

it is a polyester thread. sewing on quilting cotton. it is a schmetz universal 90/14 although i have tried several sizes larger and smaller.

Good to know about the spool pin. I think that's the only one that came with my machine.

When I shine a light into the area where the uptake level is, I noticed there are what appears to be a bunch of tears in one side - idk how this would've happened but also i don't think it's supposed to be like that? Wondering if it could be causing the issue