Exactly this was the problem. (A friend that checked the BP with “fresh eyes” saw it too :D)
Simply save the Rotation to a variable so you’re not using the already animated current rotation and it will run smoothly.
As for the Rinterp:
It seems really nice if you want to work with speed (and therefore variable animation lenghts), but you have to do more checking (when is it close to the target → from this point on animate linear or you face an exponential movement problem too as far as I can see)
I guess I try to figure out a solution for this the next time 