Pretty easy to reproduce this one.
Create new 2D side scroller project. Edit BP for the 2D character. Create a custom event called “Crash”
Find Ledge13 on the map,
Important! Set its collisions to “Overlap All Dynamic”
Turn it into a BP and to the begin overlap event, add a call to the crash custom event.
Run the game and you should fall through Ledge 13 no problem.
Now edit the custom crash event and add an argument that is a PASS BY REFERENCE to Ledge 13 BP you made.
Return to the Ledge 13 BP and add a reference to self and pass into Crash event.
SAVE EVERYTHING! Run the game and walk onto Ledge 13. UE4 asplodes!