Waterfall - Connection Issues

So, I’ve been trying to configure a PaperMC Hub, with ViaVersion for 1.12.2 clients + 1.14.4 clients to connect to (They both connect fine, tested with vanilla client + modded) and I have a 1.14.4 vanilla server linked up as well, now when I use vanilla 1.14.4 with the hub and connect to the extra 1.14.4 world, I load in fine, no disconnects, the transition is flawless.

Same with the modded FTB Revelations 1.12.2 server when connecting from my lobby world, but 2 of my friends tried joining; they can join, but after doing anything they get kicked with this error.

I assumed it was playerdata/map issues, so we wiped cfgs clean + map, but nothing has changed.

I even disabled pps in ViaVersion incase it was a packet limit issue too…

Here is my pastebin log of the disconnect/packet unable to be handled

https://pastebin.com/cUmnErbz

java.lang.RuntimeException: PLAYER target expects a Player arg at net.minecraftforge.fml.common.network.FMLOutboundHandler$OutboundTarget$4.validateArgs(FMLOutboundHandler.java:136) ~[FMLOutboundHandler$OutboundTarget$4.class:?]

Looks like you should try the metadata option in waterfall.yml, maybe invalid entity ID caused by bungees rewriting? Mods + bungee in general are pretty funky, that setting should help correct some behavior