Extreme wear on Xtreme V wheels

Hi all

I'm hoping somebody can assist me to identify the cause of why my Xtreme V Wheels are badly worn despite my Workbee only seeing several hours of use. It's mainly the wheels located on the x axis gantry, closest to the router (which I appreciate is where the main forces are applied due to the weight of the router). I'll try to upload a picture later but suffice to say some of the wheels are very worn with a complete V section made (if that makes sense).

I thought it might be over tightening of the eccentric nuts but I was very mindful of this when building the Workbee and I'm not convinced it is the cause.

Many thanks

Luke