After seeing that the Sylveon fix was included in the recent update, I went ahead and gave it a shot. However, it still only gives either an Espeon or Umbreon. Along with this, the forms for Vivillion are not evolving correctly, even in the biomes whose IDs have not changed (such as minecraft:jungle). My guess is that something in what is used to detect what biome you/your pokemon are in is broken in some way. Along with this, after removing the biome dependency through a datapack, it still priorities Umbreon and Espeon. It might be worth adding some kind of "priority" system to the evolutions, so one form is forced to take priority over the other.