If only on one side, I think you may be picking up dust or dirt somewhere during your cleaning process. If you clean side one first and then side 2 and the fuzz only appears when you plan side one, I think you may be "contaminating" the clean side somehow when you flip it over to clean the other side.
Record Cleaning Mystery
I have the Pro-Ject Record Cleaning Machine and something odd and irritating is happening lately. Every record recently cleaned has deposited a fuzz ball on my stylus. While listening the sound will degrade, I go look and sure enough a ball of fuzz. The machine seems to work good, the records look great and do sound clean but half way through the record the fuzz mucks up the stylus. Does anyone who might own this cleaner experience this as well? I trade off between Mobile Fidelity cleaning fluids and the one supplied by Pro-Ject. I also use the supplied brush. Thanks in advance.