This bug was reported by Nurulize on UDN:
UPackage::Save calls FMD5::Update at line 5918
The bug comes from the fact that Writer->TotalSize() is int64 vs the 2nd parameter of FMD5::Update which is an int32.
If the file is bigger than 2^31, FMD5::Update might receive a negative value and will crash on the final memcpy.
No easy repro. The bug happens in UPackage::Save when the package is bigger than 2^31
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-67856 in the post.