Internet slows down to a crawl until modem is rebooted.

Hello, would like some help on this issue we're having.

Modem is MB7621 w/ 600 Mbps plan - 2 Fridays ago there was a sudden outage that came back after 15 min - and also as of about 2 Fridays ago, the internet would slow down to a crawl until the modem is rebooted. the time it happens seems to be somewhat random, but consistently around 7 PM and 8-9 AM

Obviously in this scenario, every time a comcast representative tries to help, they'll ask with the classic "reset your equipment", which doesn't really help here as the network will degrade again within a few hours.

We've had this happen twice before - the first time was due to power cables rusting near our home (symptoms are clear as other electronics will start flickering or failing) - second was due to the exterior coaxial frying itself (which I can visibly verify outside) - neither seem to be the case this time.

After fixing the coaxial, the technician mentioned about there still being a large number of uncorrectables, and talked about filing a ticket, but I have doubts that it even happened, as there's still a ton of uncorrectables. (but our internet was mostly fine. rarely ever get max speeds though).

I've retightened all coaxial connect points inside the home, and the one outside is extremely tight, so I can't even loosen it anyways - All should be RG6 compression

I've tried with and without the splitter inside the home

I've tried modem factory reset.

This morning - the internet went to about 1 Mbps and then the modem seemed to have crashed.. couldn't access modem status page or internet (obviously)

Here's 15 min after boot (with splitter)

It's a common theme here for logs to show a lot of SYNC errors.

I have something to do a speedtest every hour. here's what it looks like pre-friday vs post-friday (1 data point fluctuations are pretty normal, but not when it continues). Upload speed is very consistent.

Every time you see the graph go from under 15-30mbps back to 500 is when we restart the modem (I also just notice now, we never get close to 600 ever).

Here's some bonus pictures of other large number of uncorrectables within 24 hours.

Do I just call a technician again? And cross my fingers and hope it's not a "me" problem and also equally hope that they file a ticket?

What should I do at this point?