crash on opening video monitor

an Ardour project I have been working on has recently developed an issue where whenever I try to open “video monitor” (which is needed for this project) the session crashes. (I have been working on the project for a few months and until recently Video Monitor has worked fine.) I am running Ardour 5.9.0 on Arch Linux 4.10.13 on a Thinkpad T420s.

here is command line and core dump output from a crash:

and here is my ardour session file:

also, around the time this issue appeared, another issue started where sometimes Ardour crashes immediately when I try to open this project.


update: running today’s build from seems to fix the problem.