High upstream power levels causing inconsistent lag spikes and "slow" internet

I've been noticing for the past 6 months that lag spikes are more prevalent at random times during the day.  This is seen during gaming sessions and regular streaming hours (youtube, netflix, etc.).  I didn't look into it until now.

Went into my Arris Surfboard sb6141 to check out the signal data and noticed a consistent 56-57 dBmV for the upstream power level.  Called Arris and they said anything below 51 dBmV is normal.  Downstream is 1-3 dBmV so that's not a problem.

I am connected directly from the coax box-≥modem->pc.  

Is there anything else that I should be checking out here?  Speed tests are normal so that doesn't really tell me much. 

I called Cox support as well and since I own my modem (not renting), they can't help me further unless I subscribe to their Complete Care for $10/month.  The reps also can't differentiate between up/downstream power levels versus up/download speeds.