In cases where serialization goes out of bounds, there is no check to see if the app is running in unattended mode before the message box is displayed. If the app is running unattended, such as on a build server, the message box will never be seen.
The specific locations where this can cause issues in 4.18.2 are in the following lines:
AsyncLoading.cpp: Line 7715
LinkerLoad.cpp: Lines 4231 and 4266
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-53673 in the post.