Hi Frozenfire,
I wasn’t able to reproduce this in 4.7.5. Are you using 4.7.5 or an earlier version?
To test this, I created a new Actor Blueprint and set Mobility of its DefaultSceneRoot to Static, and dropped it into level. I got DefaultSceneRoot > Mobility > Enum to String > Print on Event Begin Play. As expected, it printed “Static” during PIE. Am I missing any reproduction steps?