Symptoms
The remote control codes of some specific models of Vizio TV seem to overlap with the codes of the 840BN. Pressing the Volume Up button on these models may cause the 840BN to change inputs.
Mitigation
At the moment, placing some tape, like black electrical tape, over the IR receiver of the 840BN (the clear, circular window on the front panel of the 840BN) is the only way to prevent unwanted switching caused by the Volume Up button of the Vizio remote control. The remote control of the 840BN will not work while the IR receiver is covered, but auto-switching, and pressing the Switch button on the front of the 840BN will still work normally.