on the german mini-forum somebody had the same problem and got this answer:
"If rust has formed between the rocker arm and the brake anchor plate, this pushes the armature plate towards the wheel flange.
In the assembled state, the distance is already quite low. The wheel flange then grinds on the anchor plate.
It may happen that this is then difficult to turn, but you still can not really hear it because (only) the seal-ring (Simmerring) on the anchor plate grinds ...
So check here for grinding marks, or whether the anchor plate between the 3 mounting bolts is still flat, or already slightly curved!"
As well you could cut a shim out of the tin of a spray can an put it between the two bearings.Take the torque wrench then!
Or ask your parts dealer if he has steel shims,they are available in all sizes and thickness!
Thanks! I checked the brake plates for wear but couldn't see any, then put the hub together with a random shim in between the bearings and it spinned perfectly! That means I will need some new bearings so Cian I'll send you a message on FB with further details. Thanks to all of you for the replies!