BuildCraft version: 7.99.19
Forge version: forge-1.12.2-14.23.5.2808-universal
Link to crash report or log: n/a but see below
Singleplayer or multiplayer: multiplayer
Steps to reproduce: add the BuildCraft mod, server halts during startup with the error
Additional information:

forge server startup log ends with...
[...]
[12:04:23] [Server thread/INFO] [FML]: Registry Item: Found a missing id from the world galacticraftcore:bucket_oil
[12:04:23] [Server thread/INFO] [FML]: Registry Item: Found a missing id from the world galacticraftcore:crude_oil_still
[12:04:23] [Server thread/ERROR] [FML]: Unidentified mapping from registry minecraft:blocks
[12:04:23] [Server thread/ERROR] [FML]: galacticraftcore:crude_oil_still: 725
[12:04:23] [Server thread/ERROR] [FML]: Unidentified mapping from registry minecraft:items
[12:04:23] [Server thread/ERROR] [FML]: galacticraftcore:crude_oil_still: 4679
[12:04:23] [Server thread/ERROR] [FML]: galacticraftcore:bucket_oil: 4680
[12:04:23] [Server thread/WARN] [FML]: Forge Mod Loader detected missing registry entries.

There are 3 missing entries in this save.
If you continue the missing entries will get removed.
A world backup will be automatically created in your saves directory.

Missing minecraft:blocks:
galacticraftcore:crude_oil_still
Missing minecraft:items:
galacticraftcore:bucket_oil
galacticraftcore:crude_oil_still

Run the command /fml confirm or or /fml cancel to proceed.
Alternatively start the server with -Dfml.queryResult=confirm or -Dfml.queryResult=cancel to preselect the answer.

Can BuildCraft work with GalactiCore for Minecraft 1.12.2?

I also tried buildcraft-all-7.99.21.jar, got the error with that one as well.
jars downloaded from Curseforge this morning.

Regards,
Pat.

this is not a buildcraft issue, it seems galacticraft is not registering it's items when buildcraft is present for some reason, they need to register them or migrate them to the BC items if they don't want to have both in the world

thank you for replying.