Hi,
My understanding is that some subsystem will only be available on the node that is currently primary for RG0.
Best practice would be to deterimine who is primary for RG0 and then run your "show lacp interface" commands, "show route", etc...
Example:
node0 is primary for RG0 (control-plane)
node1 is primary for RG1 (data-plane)
You would initiate your ping from node0 because it is primary for RG0, but your ping via the data-plane (RG1) would go out via node1.
Sometime "this" works because say node1 is primary for both RG0 and RG1 or node0 is primary for RG0 and RG1. Just do your troubleshooting from whichever node is primary for RG0 and things will make more sense...
Hope this helps clear up some things...
I was actually experienceing this live this morning (20130804) during a cut-over from Checkpoint Crossbeams to Juniper SRX's... and a co-worker cleared things up for me... =_)