This is a top crash occurring for users in the 4.14 and 4.15 releases. Unfortunately no user-descriptions of the issue have been provided, so information is limited.
Despite a different callstack, this issue bears resemblance to [Link Removed]
repro steps unknown
Assertion failed: IsValidIndex(Index) && ChunkIndex < NumChunks && Index < MaxTotalElements [Link Removed] [Line: 354]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-44336 in the post.