I have a Deco M5 3-pack with one as the router (attached to AT&T fiber service 120mbit up/down) and with the satellites hard wired via ethernet.  Speed tests via wired and wireless are great in all parts of the house.  However, when using Zoom video conferencing (via multiple accounts and services, to multiple different audiences) the upload performance from my PC is consistently terrible.  Screen sharing and video outbound are always garbled. Any time of day. As a participant my downloaded content is fine, but when presenting anything, even low resolution video or images, the performance immediately drops.

I have tried:

1. setting the one device using Zoom (a PC that is wired) as the only one with 'high priority' in the QOS settings. 
2. raising the bandwidth limit. 
3. lowering the bandwidth limit. 
4. making sure no other devices are downloading or uploading anything at all. 
5. Multiple speed tests before/after. The speed tests always show 120/120.

The last thing I tried was taking my PC and putting it plugged directly into the AT&T box so it did not have to go through the Deco M5 as a router.  As if by magic, Zoom performs beautifully.  There are no issues with video, audio, or screen shares.  Clearly the Deco M5 is doing something to the traffic (not slowing it down, as a bulk speed test shows it is very fast) that is corrupting my Zoom sessions.  I am pretty sure its relaed to the attempt at QOS mediation the router is doing. I would like a way to turn the whole QOS system off entirely (or turn off whatever is causing such disruption in bandwidth consistency).