For the director…
Assuming you’ve earned your actor’s trust, there are times where the best note you can give the actor is to simply say “I don’t believe you here.”
It might seem harsh on the surface, but if that’s how you feel, then tell them. Don’t over-explain. Don’t try to solve. Just tell them.
If it’s a trained and talented actor who truly cares about the work and not their ego, then they will make the fix all on their own. And at some point, even if they never tell you, they’ll be grateful you gave them this note.
P.S. – Speaking of “I don’t believe you”, this video captures one of the most iconic moments in Rock & Roll history. Imagine getting that note from Bob!