In practice, it happens often that when leaving a table, the content on the DMD is still being shown. The reasons for this might be different: Improper scripting in VPX, VPX crashing or being terminated externally, etc.
While being in the Frontend - or moreover - when playing another non ROM-based table, this content stays visible on screen. This is a bit disturbing.
It would be nice, if the DMD is being reset to black by some criteria. Either a configurable timeout (x seconds) - this should be sufficient, as there are usually very frequent updates to the DMD while playing. Alternatively it could be detected if there is an active connection over the serial port.