Simulating in editor during runtime rendering causes an assertion to fail after rendering is done.
Repro Rate: 4/4
Tested this in //UE4/Release-4.27 @ CL#18319896 and the issue did not occur there, it is a regression!
Results: Editor crashes hitting an assertion due to an invalid External Pooled Texture.
Expected: Editor does not crash and continues after rendering out the scene.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-149630 in the post.