I just found on Xander mod page that someone had already reported it there.
Repofme said that he still didn't updated the rso config, so I guess we're gonna need to wait for him to update it :/
Just a quick question though...
After this gets fixed, will heavy-sand spawn on new generated chunks in my save game, or since I started it like that it is doomed and it will never spawn heavy-sand?
It seems it was just a resource rename so I've updated the name in todays version. If it needs spawning changes then Repofme will need to provide me more info or new config.