I have edited the names of some interface functions and compiled everything without any error. But when I start the game the interface functions do not work any more. I had to delete the whole interface blueprint and set up all the interface functions from the scratch.
So now it is working again, but every time I edit an interface function I get problems. The compiler results do not show any problems, however. Currently I am using UE 4.17.2 and I could not find any answer in google, yet.
I really think this is an annoying BUG!!
I have noticed that after renaming an interface function, all blueprints that implement the interface function lose all nodes in that function and everything has to be done again. So UE does not let us rename interface functions without breaking everything.
This is true for me as well. I don’t like that I can’t keep my widget functions organized by names.
Not sure how to search to see if there is a bug already logged for this at Epic.
Here is how I fixed this issue:
After renaming your interface function, right click on any node in the blueprint that implements the function and select Refresh Nodes. Then compile the blueprint.
This fix was tested with UE4.26 where the issue still exists (here I had renamed Interface function “Started Swimming” to “Start Swimming” and it broke the game)