This seems like a weird one to me
We have the following setup
WAN1 __________ ROUTER 1 __________ internet 1
/
MX 1-
\
WAN 2 __________ ROUTER 2 _________ internet 2
during normal operation - from the internal network we can access both devices from 10.1.1.5 can reach both 192.168.0.1 and 192.168.1.1
But when Internet 1 goes down , i can no longer access/ping ROUTER 1 even though its connect internally , or from the TOOLS on the mx device , the device is up and working and i can access if we direct connect to it