I wouldnt try and synch beats in AEFX
I would set up "timings" in PPRO and create visual ref marks.
What kind of edit are you doing?
without proper system and version information as well as details about your project nobody can tell you much.
I don't understand what you're trying to do. If you're looking at the audio layer's waveform, why would you even need a preview to be playing? Why not just look at the waveform in the timeline?
The best way I've found to do stuff like this is to lay down markers doing an audio-only preview.
Press . on your number pad to initiate an audio-only preview. While it's playing, press * on your number pad to lay down markers. (This will either be layer markers on whatever layer you have selected or, if no layer is selected, composition markers.)