PEX may get out of sync and render to the wrong buffer if a window is iconified and de-iconified or otherwise obscured and subsequently exposed. Machines with Impact graphics should also have Patch 1592 installed. Patch 1592 fixes the kernel graphics part of this bug. An input device which is added after a device has been removed during the same login session may be assigned the same device ID as an existing device. This will cause one or both devices to be unusable.
Text strings rendered to pixmaps can be incomplete.
Rendering text to a pixmap using CID outline fonts can generate incorrect results. XSGIvcListVideoFormatCombinations returns BadName error value even when the name is correct. This will cause the X server to override the monitor specification on startup. See man chantab for more details. In particular, this is necessary for the X server to advertise the proper screen size in mm.