Legacy Office COM Add-ins fail to load with New Teams

A weird one, we have 2 office Add-ins that completely fail to load if New Teams is installed, but only on AVD... Both addins work fine on laptops with New Teams.

We've had this issue since New Teams released, we stuck with classic for a bit until we couldn't, and now users of these AVD desktops use Teams Web.

However it's been ages now and users want to be able to use the proper Teams client instead of the web version. Anyone come across this?

Specifically the addins are the Infor Q&A Excel Add-in, and Open text DMS Outlook add-in.

We have other COM Add-ins that work fine, like MDS 2016 and some IBM Excel Add-ins, so it's not all of them.

I've tried multi-sessions and single session, W10 and W11, even installed Q&A on a blank image with nothing else even on it yet, then installed New Teams and it broke immediately.

Anyone had anything like this?