Issues with disconnecting while playing any battle.net game

Hello,

I am experiencing persistent disconnect/reconnect issues specifically with Blizzard games/services on my personally owned ARRIS SURFboard G54-B48D gateway on Xfinity service in [Edited: "Personal Information"].

The issue primarily affects Diablo IV and World of Warcraft. Other internet services remain stable during the issue.

Symptoms:

Diablo IV enters a “Reconnecting to Diablo IV” state after roughly 30–60 minutes of gameplay.
Reconnect state does not recover and eventually results in:
disconnect to character select OR
full game crash/closure.
During these events, the Battle.net launcher also briefly reloads or appears to lose connection temporarily.
Discord, YouTube, browsing, downloads, and general internet remain functional during the issue.
In WoW, abilities sometimes grey out and stop responding as if the server connection stalled.
Ping tests to Blizzard and 1.1.1.1 remain stable during normal operation with no major spikes or packet loss observed.

Hardware / Network Info:

Gateway: ARRIS SURFboard G54-B48D
Connection: Wired Ethernet
Ethernet cable tested/replaced
PC NIC supports gigabit+
Xfinity 1300 Mbps plan
Peak download speeds around 100 MB/s observed
No Wi-Fi usage during testing
No background downloads/streaming during gameplay
No overlays running
Battle.net hardware acceleration disabled

Troubleshooting already performed:

Rebooted modem/router and PC multiple times.
Disabled IPv6 on PC and gateway-related IPv6 features.
Tested different firewall settings on G54:
Medium
Custom
Low security
UPnP enabled.
Verified bridge mode was disabled.
Changed DNS to Cloudflare:
1.1.1.1
1.0.0.1
Flushed DNS cache with:
ipconfig /flushdns
Verified issue occurs without other devices using bandwidth.
Verified issue occurs without overlays/background apps.
Tested with ExitLag:
Session stability improved noticeably (sometimes extending past 1 hour)
However reconnect/disconnect issue still eventually occurred.
Discord and general internet remain stable while Blizzard services disconnect/reload.

Observed behavior strongly suggests:

possible NAT/session persistence issue,
firmware-level UDP session handling problem,
or routing/session instability affecting Blizzard traffic specifically.

Because the issue persists across DNS, IPv6, firewall, and local PC troubleshooting — and because ExitLag measurably improves session duration — I am requesting investigation into:

possible firmware updates for the ARRIS G54-B48D,
known UDP/NAT session handling issues,
or compatibility issues affecting Blizzard/Battle.net services.

My current firmware is 

I would also appreciate confirmation whether newer firmware is available for this gateway on Xfinity’s network.