Not sure why Rider would complain there and not on your bind axis vector. I use VS so I can’t help much there.
Are you calling the super in your overridden function?
Super::SetupPlayerInputComponent(PlayerInputComponent);
Hard to know what’s going on without knowing what object it’s looking for when it throws the access violation. I’m still on 4.26 and some input stuff has changed in 5.0, but the way I’ve outlined is how I do mouse input bindings. You could make a fresh c++ third person project and look at how the character is setup for a clean example.