Hi, there :
We’ve found a bug in blueprint. The reproduce process is :
1. Create a new Project.
2. Modify a blueprint.
3. Select “Save on Compile”->“Always”.
4. Click “Complie”.
5. Play on Mobilepreview / Standalone Game.
Wish this is help for you.
Thank you for reporting this issue. I was able to recreate this issue with ease thanks to the steps provided. I have also tested this issue with a newer version of UE4 and the issue does not occur. I am unsure as to when this this release will become public, but the issue has been resolved. If you do run across this issue in a future UE4 release, please feel free to reopen this issue so that I can further investigate.
Thanks and have a great day!