I mean, I knew I could edit the object, but I wondered if there is the permanent solution for this glitch, on the AK-47 is much more complicated.
I remember for the USP-S, few months ago, I found the old OBJ file that I downloaded long time ago and I imported it to the Blender at that time, and it was working as fine as it should be, meanwhile I deleted it somehow and I don't remember from where I downloaded it. I tried older workshop files from 2013, but same glitch appears on them also.
It's so annoying, I've asked one accepted CS:GO skin creator did he encountered similar issues, he said that he did and solution for him is that he edit the texture file later, he colors the blank spaces where glitches are appearing and that works for him. He also said that some of the skin creators edit the OBJ files for themselves to remove glitches. The thing that bothers me the most is that I had the file that was working perfectly and now I don't know from where I downloaded it, it was probably some mirror link on some YouTube skin creating tutorial.