ORIGINAL: Deadeye
I quit buying Futaba servos after nearly half of my over 30 3004's developed this exact problem. I was told it is caused by a dirty potentiometer, or 'dirty pots'. Hitec servos all the way for me from now on.
So, is the problem only (or mostly seen only) with the 3004's? I use more 3003's than 3004's, and haven't had any issues at all with the 3003's.