CAN being wierd

[bardd]

We're using CAN for the first time. We have two jaguars chained and connected to the cRIO's serial connection.
When we try to activate both jaguars simultaneously, one of three things happen:

1. Both jags work correctly,
2. Only one jag works (always the same one), the other's signal light shows it gets an "enabled" signal but no "move" signal,
3. None of the jags work.

One thing we noticed is when you change the voltage you want the jags to send as output drastically over a short period of time, both jags don't work.

We have no idea why that happens... Help would be very much appreciated.