Same here. It crashes after a few minutes of “Play in VR Preview” without any obvious reason or clear repro step. It started after I upgrade from 4.17.2 to 4.18.1. The same way, I encounter the crash mentioned in UE-51727 (Unreal Engine Issues and Bug Tracker (UE-51146)) randomly in “Play in VR Preview”.
Developping a VR game became quite painful with those crashes 