[HECnet] SIMH experience?

[Fred]

Hi all

I've moved my SIMH VAXen to a new host with a new version of SIMH (the 
current 3.11 that I found - is there a newer version?)

Main host runs Devuan Linux (yes, I'm a systemd hater).  VirtualBox VM 
hosts the SIMH instance, also running Devuan Linux.

My area router, FRUGAL, boots fine and gets adjacency with my 
Multinet-over-IP connections, that is, LEGATO, MIM, and 31.3:: as well as 
other DECNet hosts (MISER, CHEAP)

However, the connection from FRUGAL "flaps" (going up and down) quite a 
bit with local DECNet hosts as well as the ip-connection to 31.3::

I've tried eliminating the connection to 31.3:: as the culprit by turning 
off the circuit, and the connection between FRUGAL:: and MISER:: (both 
local nodes) continues to go up and down every few minutes.

I'd welcome some pointers, things to check, etc.  Is there such a thing as 
an adjacency timer perhaps I could crank up a bit?

Thanks

Fred