You can't use a solve block that way.
Why not? I think that Jonathan had worked out a solution which works pretty well and followed the vectorial approach, Adrien had tried to use.
Nevertheless I, too, prefer to set up the solve block to work with scalars, turn it into a function which then is called vectorized. Its a bit more work to separate the results when we do it that way, though. I have done it and got the very same results as Jonathan. When Rp is assigned the unit Mohm, we even get postive solutions.