Ah, thanks for catching the SDL2_mixer issue. I updated the version of the engine to a new nightly to attempt to fix some other issue [ultimately unnecessary] and it seems the version changed and caused how a lot of the sound effects sounds and looped to change. I've gone and found an older version of the file myself and fixed the upload here/on steam.
As for the other two things:
- The Hexer's ????? entry on their learnset is because they learn one of several potential skills there, based on what their highest stat at the time is. A side-effect of how I'm keeping track of the skills behind the scenes is that you can potentially double-dip on that one, allowing you to learn multiple element+debuff skills.
- That guy's more an oblique reference than anything else, and is working mostly as intended, though I've now gone and changed them to not change direction when interacted with. Don't worry about them.