When using the Media Player freezes project in a shipping build of the game, the game will freeze and the only way to quit will be to forcefully close the program. This issue is a regression.
4.17.2 - CL: 3658906 - Issue does not occur
4.18P4 - CL: 3685441 - Issue occurs
UE4 Main - CL: 3697781 - Issue occurs
Head over to the existingAnswerHub thread and let us know what's up.