put a premade map on a server, upon starting the server throws this

even though both the client and the server have the same jar/configs. if this is ignored, upon joining the client prints out [Netty Client IO #2/FATAL] [FML]: Failed to connect to server: there are 4 missing blocks and items. starting a fresh world doesn't help.
removing rftools from both the client and the server lets the client join the server without any problems. there are absolutely no meaningful logs neither on the client nor the server.

version: 6.12
forge: 2446

This issue has been marked as needing a response from the reporter for over 2 weeks without receiving one. As such, it has been automatically closed.

I need the logs anyway