In 1956 and 1968, the Soviets invaded Eastern European countries because they had deviated from Moscow's model.
Why didn't they do this to Tito? His independent inclinations are usually explained by the fact that he defeated the Germans without much Soviet help. This doesn't explain why the Soviets didn't use force to bring him into line.
Possible explanations include Stalin did not want to provoke a war with the Western allies, or that he believed it would be unwise to put his forces through another conflict before they had recovered from the Second World War. I'm ready to upvote all referenced answers, whatever explanation they propose.