Modem keeps rebooting & T3 time-outs, even after Comcast visit

For the past month, we've been having our modem restart over and over again. First started with an Arris SB8200. Figured it might have to do with the bad Intel Puma chip that I've heard some horror stories about, so we replaced that with a new Netgear CM1000v2 last Thursday. Issues still persisted. Called up Netgear, they said my channel power levels were out of range and not all of my channels were locked, so they told me to call up Comcast. Comcast came out here on Tuesday, replaced the wire up to my apartment, then things seemed to be fine for the rest of the day. They said the wire that was going up was old (hadn't been used in years).

The very next day, the modem started constantly restarting, even more than before. Every time I do anything on the internet, wired or wireless, it restarts. Called up Netgear again, and they said it sounds like my modem has a hardware problem, but I'm suspicious since this also happened with a totally different modem from a different brand. This still happens when I plug the modem into a totally different outlet (always plugged directly). I have a replacement CM1000v2 on the way right now, though, just in case. But I was wondering if anyone here could provide any assistance in diagnosing the problem so I could get some authoritative assistance from Comcast when I contact them again.

Here's some screenshots of my modem's event log and connection details that I grabbed right after one of these restarts.

Event Log (MAC address censored other than a 00:00:00:00:00 that i noticed in the SYNC errors

Startup details

Downstream Bonded Channels

Upstream Bonded Channels & OFDM(A) Channel details

Just to make it more searchable, here are some of the critical errors that show up right after one of its reboots:

No Ranging Response received - T3 time-out

SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

Started Unicast Maintenance Ranging - No Response received - T3 time-out

Thanks!