Very poor download speeds, T3 and T4 timeout errors

Hello,

I am in an apartment complex with Xfinity internet service. The last few weeks my internet has become decresingly reliable, with periods where I am lucky to get 0-2 mbps and others with frequent disconnects that last for hours at a time. After doing a bit of research it would appear I am having some sort of signal issue, as the basic troubleshooting script checking my home network that I did with an Xfinity rep didn't reveal any problems and I have some frequent T3/T4 timeout errors during periods of connectivity trouble.

I have a Netgear CM400 cable modem with 250/15 speeds normally. My cable modem should be up to the task. Here are a couple screen grabs from my cable modem diagnostics page:
https://imgur.com/a/5R4N96c 

I do not have any splitters in my unit and haven't made any recent changes to my setup (cable modem plugged straight into the wall). What would be the best way to get the ball rolling on an assessment of the signal health by an Xfinity rep? Thanks!