Ardour randomly disconnects from JACK and all audio routing lost upon reconnect

Running Ardour 6.9.0 (64) on AVLinux MXE. This happens quite often in larger projects with dense audio/MIDI/automation. Basically Ardour glitches out and disconnects from JACK (which I can see in the “Audio/MIDI Setup” dialogue), and the following error shows up in my qjackctl log:

unknown source port in attempted connection [ardour:<TRACKNAME>] 

(for all tracks, so usually around 30 occurrences of this message). And then, when I hit “Connect to JACK” in the Ardour Audio/MIDI Setup again, all my routing connections are lost: I have to draw in the routing for each track to each bus, each bus to the master, and even the master/metronome to system out.

Why does this happen? Is it a known issue?

I also seem to occasionally get this message in the qjackctl log when it happens:

internal poll failure reading response from client ardour-01 to a port unregistered event
cannot send port registration notification to ardour-01 (Resource temporarily unavailable