Recurring latency spikes every 11.5 minutes — CMTS issue

Hi, I've been experiencing intermittent latency issues and decided to monitor my connection to document it. After running continuous ping tests for 5.5 hours I found a clear and repeatable pattern.

What I found:

• 15 latency spike events recorded over 5.5 hours
• Spikes occur at precise 11.5-minute (690-second) intervals
• Spike peaks ranging from 114ms up to 973ms on the first hop past my modem
• My local gateway stays completely unaffected during every spike (avg 1ms, zero packet loss)
• First hop is normal between events (avg 9.6ms), confirming this is intermittent and tied to a specific trigger

The 690-second interval combined with only the first hop being affected is consistent with a DOCSIS T1 renewal issue on the CMTS. My local equipment is not the cause — I am using Xfinity-leased hardware.

I'd appreciate it if someone could look into this. Happy to provide account details privately.