sender instanceof EntityPlayer
Should be
sender.getCommandSenderEntity() instanceof EntityPlayer

To allow /execute commands that have /unpack in them. So they work via World Primer and most likely for command blocks also - It looks like that was someone's issue previously.

As mentioned in #41 this mod is old and functionally done for 1.12 as I have moved on from 1.12. I'm counting this as a "feature" as I don't recall why it would have been made like this otherwise and I don't want to change something that could cause issues later.

I provided some options to you on curseforge as a way to get around it that would be safer than changing how the command works.