What is the ruling on praying behind an Imam who has a physical disability that prevents him from performing tawarruk, iftirash, and prostrating correctly, while another sound Imam is available?

The prayer is valid behind an Imam who prostrates on his forehead, relying on his hands, knees, and feet, even if he leans on his side or is unable to maintain an upright posture in prostration, because sitting with the left foot under the right thigh (iftirash) and sitting on the left hip (tawarruk) are not conditions for the validity of prayer. Prostrating on part of the forehead is sufficient. However, it is preferable to pray behind someone else.