This is a good example of how Audi do some things... The RNS-E use the DIS with two CAN commands, 6C0 and 6C1, and that commands must be sended sequentially, this is not real, but a clear example (R=RNS-E, C=Cluster):
R-6C0 1 A0 C=OK
R-6C0 1 A1 C=OK
R-6C0 1 A2 C=OK
R-6C0 1 A4 C=FAIL!!
In this example the command "6C0 1 x3" has been loosed (bad communication, software bug, or any other cause). After this, the RNS-E ignores the cluster (and cluster ignores RNS-E), so you loose your DIS messages.
If you reboot the navi, the counter will initialize, and start again with this:
R-6C0 1 A0 C=FAIL!!
This is because the cluster is still waiting a 6C0 1 A3... So you have two choices to fix this:
1) Reboot the cluster and the RNS-E at same time (battery off)
2) Wait until you have luck and the RNS-E starts a good CAN sequence with the right number (this may happen in one hour or one month).
Note that this does not happen with the two top rows, because that lines only uses 261&263 CAN commands, without counter, so always works.
Nice, isn't it?