We now have an Official Issue Tracking System in place.
You are able to submit issues without registering for an account, however we suggested you create one to be able to receive notifications on issues submitted 

Go to this Link. Once you are there you will see the main page of the Issue Tracking System.

Here are the direct links to submit issues for the following Mod Packs and The Launcher

Unleveled Network Launcher

Mod Packs:
Big Sock