Left 4 Dead 2 extreme lag and voice chat issues- XBOX One

Hello,

I purchased a new XBOX One just to play Left 4 Dead 2 a few months back. I use the backwards compatible physical disk version of the game. There is always an extreme amount of lag in online multiplayer. The best connections I have ever seen are two players
with green bars and six with yellow bars, and even then the lag is insane. Connections are typically much worse, and other peoples connections seem to degrade right after I join. I play from the southeastern US.

Separately, I can only hear voice chat once in a blue moon. In the rare games where I CAN hear a player speaking, they cyclically fade in and out from no sound -> buzzing noise -> clear voice -> buzzing noise -> no sound. Happens over and over. No other
games have these issues.

I spent a fortune just to play an nearly 11 year old game, and so far it has been all but unplayable. If anyone has troubleshooting ideas beyond what I listed below or similar experiences to share I would be very grateful for input!

So far I have tried:

Every combination of removing, redownloading, and signing in/out of multiple accounts from both the XBOX 360 and XBOX One interfaces while deleting cloud data, clearing local Xbox One and Xbox 360 stored data, reinstalling the game, factory resetting and
power cycling the console, playing without signing into XBOX 360 cloud, connecting via ethernet and wifi, running all network diagnostics in settings, resetting my router, refreshing NAT type (its always "open"), removing and reinserting the game disk, and
changing every sound, voice, and performance setting in both the XBOX One and XBOX 360 interfaces.

:)