From my experience I have exactly the same problem. It wasn’t like that in the Tyros but on the Genos, any tweaks you make to a style using the mixer (voices, volume balances, spatial location, reverb etc) and save the tweaks with your registration are instantly lost if that style file is not found when you load the registration. Even if you keep the same file name but move it to a new location on your Genos, it looses all the custom tweaks you’ve done in the mixer, even if you do re-link the registration to the style file. The only solution I’ve found is to decide on the final name and location of the style file before you do any tweaking in the mixer.
Using Murray’s registration manager as suggested however does work as an alternative - you have to go in and give it the new name and location of each custom style in each registration button where it occurs, then you’ll be ok.