I have a TAC SR open but I'm posting this here in case in case someone experienced the same issue.
System is running VSX R80.40 Take 83 on a new appliance for some time and since a few days there actual losses of connectivity on one VS. Investigation network-wise showed nothing specific, but on /var/log messages this can be correlated with the creation of "messages_routed.vs1" and VS1 is the one with the issue.
There are always that kind of entries in the file.
Dec 29 17:34:09.749148 [routed] ERROR: recv(header) returns 0
Dec 29 17:34:09.749148 [routed] DEBUG: cpcl_recv: deleting peer task 0x984d13c
Dec 29 17:34:09.749148 [routed] DEBUG: peer_remove(130): Entering !!!!
Dec 29 17:34:59.681893 [routed] NOTICE: Exit routed[132332] version routed-09.25.2020-01:19:13
Dec 29 17:35:00 routed_syslog_on: Routed syslog to "/var/log/routed_messages_vs1" started
Followed by a bunch of "KRT REMNANT <routing prefix>: ignored"
Issue last several minutes after which the connectivity is restored without any specific intervention.
The start of the issue can't be linked to any specific architectural changes on the FW or the network to which it's connected.