Doubts on ghusal

I have a question regarding ghusl. I get constant doubts about the validity of my ghusl. If someone performs ghusl and then sleeps and then does salaah at night but at night time they get a doubt that if the eye and eyebrow was properly washed in ghusl or if it was accidently left dry (note this is more based on doubt rather than certainty). The person then goes to the bathroom and washes his eye and eyebrow with the niyyah of completing the ghusl. Is this valid and he does not need have to repeat his ghusl? If one hesitates to wash it due to waswasah or because he isn't sure, does he become napak again?