Robert Shaw also did not like Robert Redford. Shaw had that limp in “The Sting” because he had wretched his knee before filing began so they wrote it into the script.
Shaw said later that Redford hardly ever spoke to him and was a real SH*T, while Paul Newman was an absolute Gem and inquired all the time about his leg.
I just finished a book by Arthur Laurents entitled, "Original Story," his memoir, and he said the EXACT same thing. No, I take that back, he said Redford said not one word to him and studiously ignored him on the set of "The Way We Were." Laurents was the screenwriter. He found it strange enough to put in his memoir.