If you are powering the Reciever using the BEC, Battery Eliminator Circuit, from your Viper ESCs, then
ONE of the Viper ESC needs to have it's center red wire removed from its connector to the receiver.
OR, The switch needs left in the OFF position, or better yet, cut the switch off , and solder a small plug socket to
the two wire stubs on the ESC, and a plug to the wires remaining on the switch.
This will keep the two Viper ESC from causing each other feedback to each other through the reciever.
One, not both Viper ESC should be power the reciever. Do take a moment to verify this in the ESC instruction manual.