This is a problem I've been troublesooting for some time.
I'm trying to get sends that contain stereo mixes.
Sometimes the clients get one ear, which can be remedied by plugging any balanced cable in part-way. But it's not stereo.
There's been a host of other issues, most of which I've solved.
The mixes of the FF800/TotalMix are routed to Analog Outs 1+2, 3+4, 5+6, 7+8, and 9+10.
I use 1+2 for CR monitors, and the remaining pairs for headphone mixes.
My signal chain:
FF800 > Patchbay > snake returns > HP amp > Headphones
Seems the issue is in the cabling.
To the best of my knowledge, I am using balanced TRS cables and balanced connections, w/ one exception:
The Y cable I am using to combine the paired outputs on the FF800 to one cable that feeds the patchbay.
In fact, the signal chain could be reduced to: FF800 analog outs > Y cable > snake return.
I'm currently using Hosa Y cables that I believe to be (2x) TRS Male to (1x) TRS Female.
Again, all cabling/connectors beyond that point are TRS.