السلام عليكم ورحمة الله وبركاته I think my Imam sometimes pronounces الرهيم instead of الرحيم. I don't think he does this intentionally, but he is able to pronounce الرحيم. He leads all the salah in this masjid. Is the salah valid?

Ustadh AbdulAziz al-Haqqan

Valid in sha'a Allah, but do advise him since he has difficulty with this and remind him may Allah reward you. And if you suffer from waswas do not bother the imam or tell him anything.