mupdf is completely broken. I suggest removing it.
Hmmm, I for one can't quite confirm this this rather broad statement. I can imagine that some (e.g. more complex) PDF files won't render properly, but a (fairly) limited test I just did showed that at least some documents worked without any trouble (whilst for another one I got '... Wrong JPEG library version: library is 80, caller expects 62' warnings).
Given the fact that it looks to me to be the "smallest" PDF viewer in the repository (when taking into account also dependencies) I can't see the harm for keeping this version around.