New modem?

I have a Motorola SB6121 modem.  For the past week & a half, I've been having intermittent signal loss, usually around noon.
I finally contacted Comcast today and "Rick" stated that the issue is that my modem is far too old and is probably causing the problem.

Logs indicate around the time of the dropped signal, the following (some repetitive)
Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
SYNC Timing Synchronization failure - Loss of Sync;
No Ranging Response received - T3 time-out;
MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;

Now, I really don't know what the above indicates, and if it is in fact a modem starting to croak, I can live with that (I truly don't remember when I bought it, but I could easily look it up and suspect it's around 2-3 years old).

But, particularly if there is an issue with it, what's a good model to look at that doesn't break the bank?