[HECnet] SIMH experience?

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