An update of Tumbleweed between Mar. 23rd & Mar. 31st broke openbox.
With a fullscreen app (tried with firefox, xfreerdp, qcomicbook), pressing
Alt-Tab or starting another X11 app (e.g. xterm) from a remote ssh connection
crashes openbox with a signal 11 terminating the X session.
openbox-session is started from lightdm with autologin in my case,
it's on a laptop without an external monitor.

openbox itself has not been updated in that time frame, I have
openbox-3.6.1-3.33.
I tried downgrading the kernel, Mesa packages and other libs but
could not prevent the crashes or got unusable systems.
I also tried recompiling openbox, disabling all the configurable
options (configure --disable-xrandr ...) but also got the crashes.

When I replace openbox with twm, icewm or xfwm4, the system behaves
normally.
Can anyone reproduce or help me figure out how to debug these crashes?