Hello, I am from Croatia and am new here. I am currently building my first CNC machine and have noticed that approximately 30% of my polycarbonate extreme v-wheels does not run smoothly. When I roll them by hand, the resistance I feel is not continuous, It rather feels like crackling so to say for a lack of better word to describe it. It does not seem to affect functionality at the moment but I'm wondering if this is normal. The wheels were bought 2 years ago but never used. Does anyone have a knowledge about this?