Error this blueprint (self) is not a CharachterHUD_C, therefore 'Target' must have a connection

basically what title says i get this problem over the following snippet of script
and i have no idea what it means

uh i believe this is in the level blueprint and i have gotten this prob quite a bit but have no idea how i fixed it and i dont use the (cast to reference) way of communication between blueprints because i dont understand how to use it and how it works

I’m having the same error. Any variable I have doesn’t get used. I get the error

“Error This blueprint (self) is not a Board_C, therefore ‘Target’ must have a connection.”

This is coming from within my blueprint, Board_C. Strangely, if I have the blueprint open, the bug doesn’t happen, and the game compiles correctly. If the blueprint is closed, then everything starts messing up.