Remington Steele

In season 4, the female star was diagnosed with breast cancer and she continued to do what she could but they had to significantly curtail her parts in the shows. They had to write episodes focusing on the other characters and she was only on screen for a few minutes each episode for about the last half of the 4th season. There was also talk of the 2 leads strongly disliking each other but, just as with Castle, no one knows for sure. I do know that her health was a major issue. It was a shame because the first 3 seasons did a wonderful job of growing their relationship and leading up to a wedding in that last season.