We tried a work around suggested online based on the call stack, but that didn't seem to make a difference, based on the crash reports we saw.
Something is odd about the crash reports. We don't call glib functions in anything but the main UI thread, but all of the crash reports seem to have backtraces with glib calls in other threads.
Quite a number of the crash reports seemed to have SELinux loaded, but for more recent builds, that doesn't seem to be the case.
My hunch at this point is something about the translation layer from GTK to Qt for openbox is doing funky things. At some point I'll see if I can create a snapshot of my Arch VM and try setting up openbox to see if I can reproduce.