Unknown if this is something you're able to control, but when I have additional additions installed on my fabric server/client, and I log in to the velocity server's hub (Velocity proxy + 8 Paper servers + 1 Fabric server), all the blocks are random as hell and I'm unsure why. It could be that I'm exceeding a block ID limit and blocks are being transposed up in count, but I figured I'd report it.

Without installed:

With installed:

not an issue on our end, check if there are any mod mismatches between client/server, try asking in velocity/fabric support servers

I mean, I literally just said that they don't match. This means that your mod doesn't support proxy servers, since proxy server lobbies don't include the mods that are on the modded servers. It also sounds like you don't have an interest in understanding the issue, either, which is disappointing.

that's not something i can fix afaik

I have the same issue, only with this mod. Quite annoying really, as I can't use this mod in my modpack anymore because of this reason. Hopefully, (even though this is marked as not planned) this can be fixed in the future.