XL4 clipped program when only two tuners in use

I was recording three programs on my Premiere XL4 at 8:00 tonight. One of them was 61 minutes long. At 9:00, I recorded two programs. Even though two tuners were unused at 9:00, the last minute of the 61-minute program was clipped.



This is what I'd expect on my Premiere XL, with just two tuners. Why did this happen on my XL4?