PAC3 Items Lagging / Flashing

Hi,

This was a problem I used to have on a server of mine, and is now happening on a friends, which leads me to believe that it is a common problem for some people.
Basically, in pac3, objects will either lag and glitch around behind you, or flicker in and out of existence as you move around. Usually only other people see these problems, and for you it’s fine.
This was very annoying and people really need some answers. Has anybody had this happen or got an idea?