There are a number of arcade games that projected their video by means of a mirror. In order to emulate this setup, MAME 0.78 incorporates video flip/mirroring code that has not yet been incorporated into MAME 2003 or MAME 2003-plus.
@grant2258 spent time compiling a reference list of some affected games
There is a workaround: by using hunterk’s RetroArch screen mirroring shader users can work around this bug, but of course that is only viable for users with shader support and those with a frontend like RA that supports shaders as well.
This issue will be resolved when there is full flip/mirroring support in mame2003 (which will also get ported to mame2003-plus).
In terms of work to date, grant and @dankcushions have both put time into researching the solution. Their notes can be found here: https://github.com/libretro/mame2003-plus-libretro/issues/81
Some specific posts might be relevant: