@DarthLlama The start.sh is generated by the forge install that is run as part of the container. If it is running behind by 4000ms it seems like it may be starved for resources. The Stone Block 2 container requires 6GB of memory. I will take a look at the install again tonight and see if I can find any issues in the install script.
@RedRobo The permissions need to be set on that directory under appdata. 777 means that owner, group and all users will have read, write and execute on that directory. You need execute on a directory in linux in order to change to that directory, otherwise you will not be able to.
Opening a terminal and running
chmod 777 /mnt/user/appdata/sevtechages
will set the permission on that directory. There is nothing extra to be installed, the container downloads and installs the appropriate files for that modpack on startup. Provided it can actually write to the required directory