There has been a bug in VyOS for some time now. It occurs when the router is rebooted. What seems to happen is the route maps applied to each peer are dropped before the sessions and killed. The end result is that the session trips max prefix filters on the peer’s router and that usually requires the session is cleared by the peer before it can be re-established.
I’ve found a way around is to disable the interface before the reboot. sudo ifconfig eth6 down, then reboot.