On our server we noticed we'd get massive lag spikes for a few minutes when we all went into the Nether, but if at least one person stayed behind there'd be no lag at all. After some testing we found that the lag doesn't happen if we break our ender hopper before going into the Nether.

Minecraft 1.19.2
enderbundle-fabric-1.11.2

My modlist & system details:
https://gist.github.com/jozzo402/f4fdd50f62a686908a81bde59a428e78