BuildCraft version: 7.99.15
Forge version: 1.12.2-14.23.2.2651
Link to crash report or log: Pastebin
Singleplayer or multiplayer: multiplayer server
Steps to reproduce: unknown

java.lang.ClassCastException: net.minecraftforge.items.wrapper.EmptyHandler cannot be cast to buildcraft.api.transport.pipe.IPipe

My MP server crashed with ClassCastException. (Sorry that I've just found the server crashed and did not know who did it and how to reproduce it.)
Seems that EmptyHandler is an exception that should be handled not casting to IPipe.
Just guessing, though.

Description: Exception in server tick loop

Additional info:
I tried to restart my server but failed. It crashed again when loading the world.

I think this is caused when a tile entity returns the wrong object from ICapabilityProvider.getCapability.

Can you post the full crash report? It might have more information (like a full mod list).

I've assigned it or myself as i need to add checks for this sort of stuff internally.

(Note that this looks very similar to #4061 - without the full crash report I don't actually know if you're using bonsai trees, but seeing as how you are 2 Buildcraft versions behind it seems possible that you might have an outdated bonsai trees as well)

yes, please update buildcraft and bonsaitrees, and maybe other mdos that are outdated as well, probably will fix it

Fixed with updating bonsaitree to 1.0.4-b71!

Thanks for your support :)

Here is the full report.
https://pastebin.com/uGy65Jqk

bonsaitrees-1.0.3-b67.jar

I saw it lol.
Should update the bonsai tree mod to 1.0.4-b71 fix this problem?