I duplicated it.
Somewhere in your settings the following is occuring..
ror 1
flipx 1
You can confirm your setup by typing in command-line:
mame galaga -showconfig > showconfig.txt
Open showconfig.txt with you favorite text editor and look for those 2 lines.
You MUST have an .INI file adjusting these MAME parameters - stuff like that doesn't happen by accident. Since it's for one game, you must have a file called GALAGA.INI somewhere (probably in INI folder). Per-game .INI superceed anything in your normal mame.ini, so even if you made a fresh one, it would use the alternate .INI.