I am using the latest 1.12.2 Forge build, 14.23.5.2847 and IC2 2.8.169-ex112.
This version works fine on the client with all of the other mods installed.
Version 2.8.170 works fine on the server, however it does reproduce issue #2624 where all blocks show as Industrial TNT and have no GUI until leaving the server and logging back on. If there is a way to fix this bug and use the release build instead of this one, please let me know as that is preferrable.
If you would like to see the full crash report including all 150+ mods loaded, click here for the crash, and here for the full log.
Thank you for any help!