I would try to reinstall the Engine making sure you run it with full Administrative rights.
Regarding the crashes with 4.18, many people have been experiencing them. It seems to be more stable with 4.18.1 but still it does crash from time to time. Very likely this is unrelated from the missing DLL’s.
One thing that seemed to help on my side was to turn off the CPU Boost Mode (throttling or overclocking).