Is there any chance you did Rebind Possessable References at some point? If you did, it’s this bug Unreal Engine Issues and Bug Tracker (UE-256345) and it’ll be fixed for 5.6. The only workaround I know of right now is to click on the + button to add the camera component again in sequencer and copy the old tracks to the new component.
If you didn’t do Rebind Possessable References, I’d be curious if you have any further clues how you got to that state.
