The instructions to pause a show using SMPTE differ if you are using the timecode1 vs. timecode2 SMPTE sensitivity option.
If you are using timecode1, you need to pause the SMPTE feed first. Then, pause the 18R2. Once both are paused, the show will pause.
If you are using timecode2, you are only required to pause the SMPTE feed as this will cause the 18R2 to pause automatically.