I've isolated this as much as I can, and also posted tips in several places.
I have no other suggestions
easily killed him with trainer on, unlimited health, super damage. Cannot replicate here.
The name of the option and the description of what it does is actually fairly accurately descriptive, and working as intended.
Toggle on and it's as if you are dead. Enemies either are confused, cannot see you, react to sound, or will not do most attacks. You cannot SAVE while in GHOST mode. For STEALTH this is an easy way to get around, especially if crouched.
That is most likely because you closed the trainer and reopened it on the same game session and tried to reactivate an active cheat. Save and close the game completely and then try using that cheat again.
It helped to get away from Rhino when I had that Animal Mission.. I just beat her in the Ring,, got a mission, But she is one who cant die...