Results 265 comments of qouteall

"farsight" is a mod? Are you sure that "farsight" makes the lag spike more severe? Then please make another issue.

Do you get this issue with the fabric version?

Other people encountered similar issues on forge version as well but not in fabric version.

I cannot reproduce this issue. It does not happen in fabric version so I suspect that it's correlated with forge's concurrent mod loading

How do you get the conclusion that IP is not sending the packets? IP sends world packets. Both server and client requires the mod

Are you sure that the second client has the same mod list as the server? And post the log

Use the latest IP for 1.16.5. Other 1.16.4 mods should work on 1.16.5

Well seems that github does not show the contribution guide https://github.com/qouteall/ImmersivePortalsModForForge/blob/1.16/CONTRIBUTING.md