BuildCraft version: 7.99.18
Forge version: 14.23.5.2808
Link to crash report or log: https://pastebin.com/q7pkdLVu
Singleplayer or multiplayer: MultiPlayer
Steps to reproduce:

• Place a Helium Collector from NuclearCraft.
• Add two iron drums adjacent to the connector.
• Allow the drums to fill up to 16,000.
• Remove the Helium Collector, and put in a SuperCooler from NuclearCraft.
• Pipe via iron transport pipe starting from the right iron drum into the cooler.
• As soon as the iron transport pipe is placed over the cooler, a server fatal crash results.
• The player is unable to reconnect/rejoin, as the server will instantly crash upon his/her doing so.

Additional information:
This is currently keeping a player from rejoining our live server. As soon as they do rejoin the server, the entire thing just crashes out on everyone, The client that caused the crash also experiences a game crash on their end.

Kindof, it seems they use some checks to determine if a given capability is related to mek's gasses?

However they added a "try...catch" around the call at some point, so what version of NuclearCraft are you using?

Version 2.12e

Was curious if this was able to have been reproduced as of yet?

seems this got missed, sorry

but looking at the crashlog this is a nuclearcraft issue: Caused by: java.lang.IllegalStateException: You must provide your own instances of interface buildcraft.api.inventory.IItemTransactor

they are not providing an valid IItemTransactor it seems when BC asks for one

I'm the server host and this is the co-owner. Any updates on the above?