Watching a program that is being recorded

I used to be be able to "watch now" a program that was being actively recorded without making it stop recording. Now it seems everytime it stops the recording at the point where it was when I started watching it, e. g., 24 minutes,  and I never get to see the end of the program. How can I start watching in the middle of a recording without stopping it? Very frustrating. I know this has worked before.