Connection dropping during large downloads.

Hi everyone, I'm having a problem with my home network and I don't know how to solve it.

I have a Cat6a cable that I bought about 4 years ago connected to my router/modem. It was working perfectly until I did two things: first, I changed my computer case, and I ended up messing with it a lot, which loosened the connector; second; I replaced my old power supply with a new one.

Well, here's the problem: when downloading something very large for a long time, for example, 250GB+, the internet completely stops working. The router/modem stays on, but there's no internet, neither wired nor Wi-Fi. It only comes back if I turn it off and wait a few seconds before turning it back on. My contracted transmission speed is 80MB/s.

I tested with another cable I have, a normal Cat6, and this problem doesn't occur. Seeing this, I thought the loose connector was the problem, so I replaced it, but the problem persists. Any ideas on what to do? Has anyone else experienced something similar?