Hi
uhm, you seem to have a lot potential trouble, if you are using photon, you should check the example provided with PlayMaker port ( on the wiki) and see how I implemented the lerping, maybe this will help you find out what could go wrong.
It could be that you slaved instance isn't totally switching off control to let the synch variables do their job. Or maybe there is a conflict between the various update times ( maybe you should try on late update).
Bye,
Jean