(Zmod3) What am I doing wrong? UV Map affects SINGLE polygon despite selecting all by material

[M A R I N A]

Name says it all. I follow this: https://forums.gta5-mods.com/topic/7670/tutorial-zmodeler3-how-to-make-uv-template-livery-template-too to a T and majority of the time it just affects a single polygon or sometimes a single polygon in the wrong material. Also might be worth mentioning that sometimes it'll work and the majority of the time it won't. Any help is greatly appreciated, thanks.