On slackware64-current, I am getting a segfault when closing Firefox with $DISPLAY set to a remote machine.
[4367] ###!!! ABORT: RenderFreePicture: RenderBadPicture (invalid Picture parameter): file /tmp/firefox-51.0.1/toolkit/xre/nsX11ErrorHandler.cpp, line 147
[4367] ###!!! ABORT: RenderFreePicture: RenderBadPicture (invalid Picture parameter): file /tmp/firefox-51.0.1/toolkit/xre/nsX11ErrorHandler.cpp, line 147
Segmentation fault
The crash is very reproducible. It happens only with a remote display.
Ed
ETA: I see that a bug has been filed
https://bugzilla.mozilla.org/show_bug.cgi?id=1335827