This is a trending Mac crash coming out of the 4.18 previews. Most of the project titles experiencing this crash mention "AR"
It is the exact same callstack and crashgroup as
UE-46421, but that was confirmed to have been fixed in the 4.16.2, and this has only just resurfaced in 4.18.
repro steps currently unknown
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-51169 in the post.