Currently, MPV propagates most of its inputs, which is not correct. When MPV tries to propagate a different version of a dependency (like ffmpeg) that is a different version what is currently installed, Guix operations will fail.
The source code in video.scm says that the inputs are propagated so pkg-config will work, but that is not a valid reason. The pkg-config file should be patched so that pkg-config will work without unnecessary propagated-inputs.
