Nothings broken, you just need to limit the mmd blendshapes so that they work with your new default face. The only way to do that is remake them. Theyll be at the bottom of all the blendshapes on the head in japanese.
Found the file on my own for those two watchers. someone archived it here already: https://archive.org/details/dizzy__mmd_download__by_thelupusboreas_dgeq64l