Since I was shooting at a target overlapping another I didn't realize it does automatically cycle targets. But It sure enough did veer off after a Su-27. I know because it was a friendly I was on comms with and was looking at the map. I told him to turn off his radar because he was oblivious. It would have come close to hitting him if I didn't tell him to turn off his radar. The missile died not far from him but failed to track after going nose cold. I also saw that B-52 / HARM incident and it was scary similar.