Nomad on Mac Mini intermittently stops sending sACN

I'm running Nomad 3.2.7.18 on a 2012 Mac Mini with 8GB of memory.  I have a Gadget with 2 universes and I'm sending two additional universes to Pathport Uno interfaces.

Most of the time it works fine and I get the correct outputs on all 4 universes.  If it matters I have a 1024 address dongle and I'm using 1006 addresses across all 4 universes.

Intermittently the Pathports will individually stop receiving sACN - the display changes from "LiveOut" to "IdleOut".  Usually it's only one at a time and the other one is fine, but sometimes both will go out together,

I put a laptop on the same network and Wireshark shows that the affected universe is not being sent over the wire, which explains why the Pathport can't see it.

Are there any special network settings required to ensure that a Mac Mini doesn't mishandle sACN network traffic?

Thanks

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