if using special frame !right (e.g. #slider.!right) and no neighbours.r is given, it will give an exception.
the actual problem is that the frame name is taken form neighbours.r which is undef and if the frame name is still undef the code will try to resolve the path “!right” which is giving more than one path-> exception (all in layer view.getFrame)

this is not a big problem as no transition should be run anyway, but this should be caught anyway
this most likely happens with the other directions as well.