Took your suggestion. Contacted my ISP. Wasn't overly impressed with the tech support but went along with it anyways. I was suggested to Reset the Cable Modem interestingly enough. So I did that and after it restarted and I got back logged into its GUI again, the modem's log was obviously much shorter and it didn't have the same errors as before. Only three entries in it still at this point, an hour and a half later (attached).It's not entirely conclusive but the "SYNC Timing Synchronization failure" errors look a bit worrying to me. I would definitely reboot the modem in any case. But I'd also contact your ISP and say you're having connections problems. They may be able to detect a fault on their side.
They've told me they think my internet drops may be the fault of the modem and not my router. I do have an old modem, a TP-Link TC7650, which I specifically bough at one point due to reviews that it's chipset had lower latency than other options.
Anyways, I've been asked to keep an eye on this for a couple days and if happens again where my internet is down while the modem and router both appear to still be up and running, I'm to call the ISP at that time before any devices being rebooted. We'll see, I guess. Could it be that the NVRAM thing isn't the problem after all?