The one on the right has a separator bridge only about 10mm while the rotating head on the left is about 20mm. So if two PAMs were to sit in the slots on the right head, they will definitely knock against each other. The same two PAMs sitting in slots of the left winding head will do better when placed with its crown facing outwards.

So the next time you shop around for a winder unit, measure the centre separator. It must be at least 20mm thick.