Please lubricate your wind cups with a spray lubricant or graphite powder. To lubricate, put a very small amount of lubricant on the axle near where the axle meets the house and turn the axle to get it down inside on the bearings. Please let us know if the issue continues. Thank you.
I have the same problem, my system is about 2 years old. I tried to remove the wind cups from the shaft but was not able to. I'm afraid of pulling too hard and breaking them. The bearing seems to be wearing out. I think I will need to replace my upper assembly.
I noticed that they sell an upgrade to the pro with two solar panels for $30. It includes the whole wind cups assembly. Mine let loose and started working but if it happens again I think I will purchase that.