I'm not entirely sure what a keyframe is, but what happens is this.
I play my movie, adjusting the audio mix sliders as I go along. At the end, I click save. I replay the movie, and find that it hasn't saved any adjustments to the audio mix. I tried sliding the sliders for 5 seconds then clicked save, but it still wouldn't save it.
I've had this problem before a few months ago but I don't remember how I resolved it.
Here is a look at both the Audio Track, and Audio Mixer in PrE 11.
Audio Mixer can work in two ways:
To test the second method, play back the Timeline, and the Slider (for the Track that you adjusted) should move on its own.
Yes, what happened for the last few months was exactly what you discribe in method 2. Yesterday, when I played the timeline and finished adjusting the sliders, I click save and play it from the begginning. The sliders stay at the 0 like they havn't been adjusted at all.
That is odd behavior. It sounds like the original Track Keyframes are stuck, and are not being replaced, as they should, with the Audio Mixer.
As a test, Select all of the Clips on that Audio Track, and drag them to an empty Audio Track, say Audio 3. It might be required that you Create Audio Track, depending on what you have already used.
Once Moved, use the Audio Mixer, as you need, and check to see that it IS placing Track Keyframes, as it should.
Good luck, and let us know how the test works out.