I came across a weird issue where the Engine would crash in FMaterial::GetShader if the scene being loaded has a translucent material assigned to a mesh, and an atmospheric fog. A temporary solution (that worked for me) would be to remove the atmospheric fog.
Unfortunately, I haven’t been able to replicate this issue in a blank project.
Technical details :
After spending a lot of time on debugging UE with the source code, I figured out that the mesh shader map inside the material only had 21 shaders rather than 44 shaders like every other material. In my opinion it sounds like shaders were partially compiled in the material.
For Epic developers : I can either send a dmp file of the crash or give you an access to my project (which is relatively big) so you can easily replicate this bug.