Strange Colour pop on level load

Hello, so i am currently working on my final year project for university and i have this really frustrating issue, on level load in the built version of the game some of the textures appear the wrong colour and then after a short pause, they suddenly all correct themselves. it can be seen in this video of the menu at around 5 seconds:

I really can’t work out what is causing it, my current suspicion is it is linked to the fact that the models use an atlas texture to get their materials, buti have no idea, it also seems to only affect some things which in my opinions writes off post process or lighting issues.

Any ideas? thanks.