When adding a variable of collision profile name type to an actor(as editable), its value gets reset when the instance becomes a part of multiple selection.
Collision Profile Name is now set to No Collision (and it will appear as such when you individually select the actors you had changed).
1. Open attached project(it contains several instances of a BP actor with an editable variable with Collision Profile Name type)
2. Change the collision profile name property of each instance to BlockAll
3. Select multiple instances
4. the collision profile name property for the selected actor is now "NoCollision"
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-46242 in the post.