If you experience this crash, please log a bug report on the UE4 Answerhub and reference this ticket number so we can discuss this issue with you.
This is a common crash on Mac in the 4.16 release.
The callstack is fairly generic , so it shares similarities with other Jiras such as [Link Removed] and [Link Removed], but this issue is different.
With Xcode 7.3.1 ([Link Removed]) installed to /Applications/Xcode.app, download attached 8650_51197943.metal shader to Desktop, then execute following commands from the terminal:
First command will succeed, but the second one will fail with the metallib: Unexpected token !r error.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-45463 in the post.