What happens when an encoder goes out?

[Inconceivable]

Hello! I'm am using a CAN based (speed mode) control this year for a mechanum drive equipped with the us digital E4P encoders that come in the KOP (with 360 encoder wheels), and a mentor brought up a very good question. What happens if an encoder stops working or malfunctions? My gut feeling is that with all the safety checks implemented in the CAN Libraries (Labview), The Jag would figure out that it's not getting a valid signal from the encoder and simply shut down, but is there the possibility that it would just go full speed ahead in attempt to get to the set RPM (because it's reading 0 RPM)? If a Jag can detect whether or not an encoder is out, and one does, I intend to have all of the drive-motor jags switch to voltage mode so you aren't stuck with a dead wheel, or robot, depending on how it reacts... Does anyone know?