H.264 crash in media encoder beta 15.1 converting high bitrate from premiere prores 422 62gb 1:17 hr

Steps to reproduce:
    1. drop in prores 422 62gb 1:17 hr long export -chose h.264 high bitrate and started process
 
Result: ...hard system crash and reboot - was the same crash result as release version 15.1 of meadia encoder encountered earlier in day
Expected: ... hoped for same result as h.264 med bitrate export which completed successfully in beta but not in release version

I had just made clean install of OS Mojave on reformated HD few days earlier
 
System info
    Application: Adobe Media Encoder (Beta) v15.1.0.28
    OS: macOS v10.14.6, RAM: 128.00 GB, CPUs (logical): 16