Hi,
I had to zip the log as it was too big to be viewed on gist via browser.
https://drive.google.com/file/d/0B2k5QuMv5TYjYW1neFlPOExIYzA/view?usp=sharing (fml-server.log)
Error in question starts at line 96396:
It's a private modpack. This crash only happens when certain players logout, and it happens with both Java 7 and java 8.
The client freezes and then disconnects, and the error is received on both client and server, then server crashes. Unable to reliably reproduce. The server and client are both always within their memory restrictions.
If all you can do is rule out forge as the culprit, that's fine too.
Thanks