So your issue is most likely the close proximity of the Router to the MC3 processor in a Metal Equipment Rack.

Page 15 of Crestron's Best Practices For RF as referred to by PeterN earlier in this thread is dead on correct and should be your bible.

At least 12 feet from all other gateways on adjacent channels, and 6 feet from all other gateways on NON adjacent channels.  This has been my no compromise rule on ANY RF producing devices near the area of each other.  This also includes cordless phones.

A great test to prove this out would be to remove the MC3 OUT from the equipment rack, to somewhere else, perhaps outside of the Mechanical Room....plug power in and an ethernet cable to connect to your LAN there, and then sit on SIMPL Debugger/Test Manager and watch as you test the Remotes.

I'd definitely move that Router clear away from that equipment rack, at least 12 feet away from that MC3.  In addition, I would also consider getting a dual band Router (for 5ghz), or getting a non-wirless router, with a WAP you can remote locate away from that area.

Good Luck!