I am using the latest AP 8.1.0 on a Windows 64 bit computer. For a software simulation where I am capturing the screen for a walk-through of an HTML 5 web-application using system sound (running on my computer in a local FF browser window), this app has some sections video/audio and some video with no audio. I noticed that once the audio stopped, no further video was captured. So, if no audio, no video capture. At first, I solved the problem by separately doing a video recording on the no-sound screens, then copied and pasted into the first (software simulation) capture project.
I think that I solved this: after further experimenting, instead of using software simulation, I used record video, which allowed me to record the app’s screen and sound completely.
BTW, recording quality (video and sound) is excellent.