Reparenting a blueprint to another blueprint that contains an event dispatcher with the same name as an event dispatcher in the parented blueprint shows warnings in the child blueprint and prevents the event dispatcher from being modifiable.
Steps provided by licensee:
1. Create two blueprints. Give them both the same event dispatcher (OnHelloWorld, for instance).
2. Now, pick one of the blueprints, and reparent it to the other one.
Compile warning appears on screen -
"No Delegate property found for OnHelloWorld
No SignatureFunction in MulticastDelegateProperty 'OnHelloWorld'"
OnHelloWorld cannot be modified or deleted
Blueprint compiles with no warnings, OnHelloWorld can be modified/deleted.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-26817 in the post.