In addition to Monroe 's problems , Montgomery Clift was often unable to perform due to illness . By the final day of shooting , Thelma Ritter was in hospital because of exhaustion . Making the film had proved to be an arduous experience for the actors ; in addition to Monroe 's distress , Montgomery Clift had frequently been unable to perform due to illness , and by the final day of shooting , Thelma Ritter was in hospital suffering from exhaustion .