I may be misunderstanding the purpose of lesson play presets but to me It seems as if there is either a button or strategy missing on the main dialog because using the presets means that some lessons do not play if presets are used.
1. with setting preset 1 = vocab review like picture below,
2. enter a lesson like "to know" in intermediate ( sorry the app does not show lesson number like the website)
3. Press play and the play button will "circle" but no audio plays.
I suspect that it is because this particular lesson has no Vocab review. If you exit the lesson, reset setting-play presets to nothing, then reenter the play button will give a choice between lesson or video.
A. I suggest that the correct behaviour should be - When is no content of the desired play type in the lesson you have manually entered, it should give you the remaining choices just like no play presets.
B. There should be a button on the lesson play to allow you to select which number of the lesson presets you have selected, so that you can change them form within the lesson. Otherwise there is no point in having multiple preset options. Perhaps it would be better if you just coded these to show a new button next to the play button containing one letter like A,V, L, D ,R meaning All, Video, Lesson, Dialogue, and Review respectively, so code numbers do not need to used and assigned in the setting page at all. That way the button could just show on the lessons page rather than the setting page which is not accessible while in a lesson. Note that I have suggested that you include an All tag which is intended to show all (ie. exactly the same as having no preset at all.
C. I have assumed, but not checked that the automatic playlists that generate after entering a lesson do check that the appropriate type content exists and excludes any that do not have that content type. eg. with play preset set of Vocab Review, I would expect it to only choose lessons with Vocab Review data so that case A does not occur with others in the playlist.