[CABill]

Since you have two remotes, why not just swap the batteries between the two as a first troubleshooting plan? The remote itself sends the signal that voltage is low - it isn't the receiver saying anything about the received signal (through whatever). The one remote could happen to trigger the message with a lower voltage than "normal", or it could be true that the batteries are really low! No matter what you see on the meter, a current load could drop the voltage.

Just putting in new batteries would be a good test. So would putting the receiver into single mode and bringing the UHF remote into the same room as the receiver. You should see occasional low warnings when the remote is 3' away from the receiver if the remote is just notifying the receiver that its voltage is marginal.