Vins I had a similar issue when I upgraded! Seems to affect a very limited few. I was going crazy until I figured it out. Maybe this will work for you:
Did you have any core remaps? I did and it loaded it for all systems in 34, messing things up. Delete (backup first) any remaps in:
\\batocera\share\system\.config\retroarch\config\remaps\ (notice the first .config)
and delete the old custom retroarch config in:
\\batocera\share\system\configs\retroarch\retroarchcustom.cfg
Try restarting and see if it works.
In v34, any new remaps will get created in a different directory:
\\batocera\share\system\configs\retroarch\config\remaps\ (notice configs with no dot)