Robert Shaw and director/producer Mark Robson passed away during post-production. Both died of heart attacks within months of the other; Robson in June 1978 and Shaw in August 1978.
Robert Shaw was very ill during filming and died during its production. His voice was so weak and his delivery was so shaky because of his illness that his voice was dubbed by Robert Rietty, although Rich Little also dubbed three words near the end of the picture ("Harry, come on") and six words in Shaw's own voice were deemed usable ("Too hot in that train" and "Harry"). Little insisted he not be paid, as he was a big admirer of Shaw.
According to several sources, the last two days of filming, following Mark Robson's death, were actually directed by the film's cameraman Jack Cardiff, who had directed several previous films (winning an Oscar nomination for "Sons And Lovers"). Monte Hellman may have re-filmed some scenes at a later date, but his chief function on the film seems to have been as an editor and a supervisor of post-production. The filming had generally been chaotic, and complicated still further by the sudden death of leading man Robert Shaw before he had post-synchronized any of his dialogue. Hellman's handling of the extensive footage would seem to have been drastic; certain well-known actors appear only very briefly (one of them, Vladek Sheybal, is billed under another name), the action is often elliptical and the plot is mostly confusing, whilst dialogue is often sparse.