@ChrisMack Thank you for your report! I’ve opened an issue on the SpongeVanilla repo for this and will look into a fix soon:
SpongeVanilla is pretty stable already, pretty much the only thing it is less stable in are rare cases like this one that don’t get noticed as fast as on SpongeForge because there are less people currently using (and testing!) SpongeVanilla. However, there is no need to suggest against using SpongeVanilla if no Forge mods are needed.