High Latency Under Load / Bufferbloat – Need Help Escalating (DOCSIS 3.1, Smart Queues Enabled)

Hi Xfinity team,

I'm having persistent high latency under load, and I need help escalating this issue to Tier 2 or Engineering if possible. Unusable internet

📍 My Setup:

• Modem: Leased Xfinity XB8 Modem 

• Router: Ubiquiti Gateway Max (with Smart Queues / SQM enabled)

• Plan: 1.30 Gbps down / 40 Mbps up

• Modem is in bridge mode, and my gateway handles all routing. (have tired out of bridge mode also)

• I’ve verified correct provisioning (upload was capped at 20 Mbps until recently — now fixed).

⚠️ The Issue:

• Latency under load is consistently high:

  • ~120ms added latency during download activity

  • ~1335ms added latency during upload

• Idle latency is not the best (~30ms)

• Waveform bufferbloat test confirms:

  • Bufferbloat grade: F

  • Web browsing and VoIP mostly fine, but video conferencing and gaming suffer

🔍 What I’ve Tried:

• Full modem/gateway reboot

• Tested multiple devices (wired)

• Disabled DPI, tested different DNS

• Confirmed no bandwidth throttling or local congestion

• Latency issue is worse during peak hours (evenings), better around 2–3 a.m.

💬 Request:

Can someone check if:

• OFDMA upstream is fully enabled on your end?

• My node is oversubscribed or experiencing congestion?

• There’s any way to escalate to Engineering or have my signal path/node reviewed?

I have tired other modems like the Arris S34 and the Hitron CODA56 and they had better latency but still extremely high and unusable. This has been happening for months and I had a Xfinity technician come out today and he said to use the Xfinity modem and it has gotten even worse, all he did was change the ends of the COAX cable and check for noise he said nothing should be wrong. also shown is a screen shot of my Ubiquiti Gateway max and the ISP health showing terrible disconnections and high latency. 

I'm happy to provide account info via DM. Just want to get this latency under control — speeds are great, but performance during real-time activities is inconsistent.

Thanks in advance!