I've been messing around with the new libretro feature in KODI and everything was going well until I tried using some MAME roms with the MAME 2010 core. It would either act like it was about to start or show me the compressed contents. I have no clue what I might have looked over.
Seems an older post in regards to the FBA core had the same issue. Lead me to this solution
https://forum.kodi.tv/showthread.php?tid=164725 under update. I use windows so it had to be placed in the user>username>appdata(hidden folder)>roaming>Kodi>userdata <----place there. Didn't quite detect everything but still worked out pretty good.
More general details of where to find the
userdata (wiki) folder are on the wiki.