When teleporting to a new dimension using multiverse or another related plugin, Multiconnect does not seem to accept the bungeecord/multiverse world and drops the connection instead right before the player can see anything on where they even are now at.

This issue also applies to hypixel when warping to a new bungeecord server of any kind.

I believe I was experiencing this too. For me, the issue occurred when respawning in dimensions without height and min_y set (servers from before those fields existed). I worked around this in my mod by creating a temporary thing that added these fields and meant to report it but never got around to it. My error was Failed to decode: No key height in MapLike.

Are you using the snapshot version?

Are you using the snapshot version?

I am indeed using the exact version as described in the snapshot branch including the latest snapshot at time of writing this comment.

Please note that hypixel is not supported on the snapshots.

Please note that hypixel is not supported on the snapshots.

Not quite as true since your mod still sets the version protocol to 1.16.4/1.16.5 so that snapshot users can connect, but the new dimension connection drop still applies in this section.