I have two of my CS:S models that don’t work completely correctly. My GSG Counter Terrorist model and my Arctic Terrorist model “disappear” after saving a map I put them on and then load it back up. They are physically there like I can run into them and if they are on the ground I launch into the air and other objects interact with them. They are not visibly there though. The remover, material, color etc tool don’t work on it. Sometimes the duplicator works though.
If you really need my computer specs just tell me although I don’t think it matters in this case.