What is the ruling on repeating the letter Raa (ر) in the remembrances (adhkar) of prayer, such as during standing (qiyam) and bowing (ruku'), and what is the effect of that on the validity of the prayer?

If a person is afflicted with [religious] obsessive-compulsive disorder (waswasa), they should ignore the waswasa and not pay attention to it. They should recite the remembrances (adhkar) and verses naturally, knowing that repeating the letter 'R' (ra’) in prayer does not invalidate it, whether it is in Al-Fatiha, the opening takbir, or during prostration and sitting.