Rotor unit is the part which fits into your motor block, this part typically has an impeller which is spinning and pushing your water. Since I replaced mine, I have no issues.@ibondy I am having the same issue with my skimmer not restarting on its own. I have an eshopps S-120. It only restarts when I raise the skimmer so that air hits the venturi entrance.
If I may, I am a noobie, can you tell me what is the "rotor unit"? I'll try to see if replacing that would fix it. Thanks.