Since a few versions the client in a multiplayer game is throwing repeated NPEs during light updates.
I could not track it down to a specific mod yet, but two occasions where I can reliably reproduce it are turning on a Modular Router (when the lasers show, the NPE pops up) or putting lava into a Dimensional Storage tank. There are more occasions though that are not as easy to track down.
Another occasion was to do with a Create gearbox. Removing that one gearbox (out of 7) stopped the NPEs from happening in that area, all the other ones had no impact.
I've already tried disabling client mods having specifically to do with rendering or with light, but with no success so far. (And before anyone asks, it's not Java 18. I did a test run with Java 17 and the error is identical.)
A full log is at https://mclo.gs/I4QMjFH - with the offending error here, beginning with
[06:15:36] [Render thread/ERROR] [minecraft/BlockableEventLoop]: Error executing task on Client java.lang.NullPointerException: Cannot invoke "net.minecraft.world.level.block.state.BlockState.m_60734_()" because "p_46606_" is null
After a while I don't get a fill stack trace any more, just
[05:20:50] [Render thread/ERROR] [minecraft/BlockableEventLoop]: Error executing task on Client java.lang.NullPointerException: null
This then happens over and over again, about twice per second until I leave the area.
Searching the internet for `"net.minecraft.world.level.block.state.BlockState.m_60734_()"` nets very few results.
Right now I'm mainly concerned with tracking down the offending mod in the first place.