This problem seems to stop at Check in HLSLMaterialTranslator.h. If the same value is entered in MCT_Float and MCT_Float4, it branches to True with IsIdentical, but it seems that a problem has occurred due to type check.
[Link Removed]
It crashes by creating a material like the image below.
[Link Removed]
[Link Removed]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-67415 in the post.