Shouting in sleep. Someone advise pls.

My father is a diabetic and he is on medication. He has been suffering with a very peculiar disease which is shouting and random movements of hands and legs. He has various nightmares and he thinks that he is physically involved during that which tires him off. He sometimes even throws items while asleep which is causing himself to inflict injuries on himself certain times. We have shown him 3-4 doctors in past 5-6 years and this problem has only aggravated. Encronate Chrono is the tablet almost everyone recommended but the effect remains only when he takes it. The moment he stops the medication the problem is back. By what I came to know from one of my co brother who practises IM at US is that this is not a neurological problem though an associated one. He suggested that my father could suffer from a condition called RBD or RDB or REM Sleep disorder (sorry i dont remember the exact words he told) He asked me to consult a Sleep specialist and said can be cured. Can someone advise pls.