look like virtul chassis has splited due to switch reboot with different OS.. or other reasons. that we can find out only to verify the logs in routing engine member. Can you provide the logs from master member.
>show virtual-chassis staus
>show virtual chassis vcp-ports
Can you verify the all member Junos OS is same or not. becuase in VC version must be same. Some time switch reboots with secondary version and that might be a diffrent OS.
OR
And can you verify alll all VCP ports or PIC slot ports as per device VC connnectivity.