Sidechain busses working inconsistently

Audition 25.0.0.47 on an M3 Max MBP

For ducking voices on a three way interview.

I created 3 stereo tracks and 3 mono busses. Track 1, Track 2 and Track 3, Bus 1, Bus2, Bus 3.

On each track there is an instance of Izotope Neutron 4 Compressor in FX slot 1.

Bus 1 Send 1 is routed to Side-Chain>Neutron 4 Compressor (Track 1 - Slot 1)

Bus 2 Send 1 is routed to Side-Chain>Neutron 4 Compressor (Track 2 - Slot 1)

Bus 3 Send 1 is routed to Side-Chain>Neutron 4 Compressor (Track 3 - Slot 1)

Track 1 Send 1 is routed to Bus 2

Track 1 Send 2 is routed to Bus 3

Now when I try to Route Track 2 Send 1 to Bus 1, the only option available is Bus 3, I can't send to Bus 1, and if I send to Bus 3 from Track 2 I can't send to any bus from Track 3.

So Bus 3 is now getting audio from Tracks 1 & 2 and sending that audio to the side-chain input of the compressor on Track 3, as expected, but the other busses are only getting one input each. It seems like the sends are disabled because Audition thinks that there's some kind of conflict or potential for feedback, but sidechain inputs effectively become control signals; there's no potantial for feedback.