This is Scrivener 3.0 on a MacAir with 10.12.
For multimarkdown processing that calls multimarkdown, if the program doesn’t read the piped Scrivener output (e.g., because it crashes on startup), Scrivener exits quietly with no crash report or any other sign of untimely death. That it doesn’t exit well is indicated by rebuilding indexes the next time.
Obviously, the new processing feature avoids the problem, but a faulty mmd installation could cause some confusion. Not urgent.