UI Error and Muzzle Flash issue

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I've recently downloaded the Mod Tools for Bo3 to create custom zombies maps. Admittedly, I used to do this with WaW in the past, but it has been 10 years since I last touched it, so I am rusty, but not a total noob - just not used to BO3 tools yet.

I followed this tutorial https://www.youtube.com/watch?v=XjPirs0Miuo but the moment I load my first map to test it, the pack a punch weapons are missing their muzzle flashes. Anyone know how to fix this or can direct me to someone who I could ask? This is affecting every other map too, not just mine. It's like the file for upgraded muzzle flashes was just erased out of existence from the game's files.

I also followed this persons tutorial on adding perks, but I now have the infamous "UI Error 41437" when loading the map. He says in the video that removing Who's Who fixes this issue, but it doesn't.