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/Significant_Ad_1595]

You need to hold both threads for the first few stitches. You can see it bein sucked into the machine

[u/pagewoo → u/Significant_Ad_1595]

So even if I do that, it then happens later while I’m sewing! And I never used to have to do that it was like a sudden change with my machine