I recall sometimes Ardour/Mixbus can even fail to start the first pop-up dialog if a plugin caused a crash just previous. A problem I was having awhile ago, was a session crashing due to a faulty plugin, and the end-result was that the application would not even start later(the plugin in question finally got fixed by the company and now works correctly with Ardour/Mixbus so this is good)… though I haven’t yet fully uncovered what was causing the application to fail, the issue was pointing to corrupted configuration rather than session data. I tried removing things from ~/.cache/mixbus5 (there’s an ardour5 path as well), … I don’t think that made a difference, so I figure I can keep an old/working copy as a backup to compare to in case this rare type of a bug happens, though it would have to take a program crash, and that is more rare as the plugins I have filed for repair are no longer crashing. I make a backup of my configurations just in case. – I suppose the same thing can be done for basic session configuration data – should there ever be a crash/corruption happening, the user can use the commands diff, etc… and maybe spot 1 or 2 things out of place…
IIRC I think erasing the plugin cache somehow had a positive efffect for a problem I was having regarding a session-load issue. You can remove ~/.cache/ardour5 which contains the plugin cache – and possibly also the ~/.config/ardour5/plugin_statuses file, and then see if your session is able to load. You would want to run a plugin-scan before loading that session of course (open a “blank session” and do a plugin rescan)-- and maybe by chance this can help.
It would be better if Ardour provided diagnostic tools to run against the session data folder to show where there is invalid data, as I think this can help for certain cases. I don’t think the auto-recovery would work correctly for all cases, and the user can apply their own fix along with the help of such tools. Currently I am not doing any large sessions, as I am still kind of learning bits of working with the daw, …though eventually I would like to learn of ways of doing recoveries that are better than what I have in mind of backing up basic session data from time to time and run a comparison test to see what configuration files may have gotten corrupted. I’m not sure why there are no such tools, I think it can be very good if such a tool was available.
hope this helps