I am using JWM on the Raspberry Pi. Version 574 is ok. With 579 I am getting occasional flicker and one crash.
It seems to be random, the screen goes momentarily blank then redraws and everything continues as normal.
I was changing the desktop icon-set, which does a "jwm -restart" -- ~/.xinitrc is setup so that jwm is the last thing executed, so that when jwm exits, so does X. Well, the -restart caused X to think that jwm had exited, and it exited X also. Or, it seemed that this is what happened, judging from the X log.
I have reverted to 574 and have been repeatedly testing, cannot get any of the above to re-occur.
Note that the Raspberry Pi is very slow, which may be a factor here. Something to do with the xrandr code added after 574?