Does the audio get kind of choppy? Also did you hear a bell before or after the game froze?
I proceed through the tutorial as normal. The audio never has any noticeable degradation. Once the potion is fully brewed I hear two chimes, with different tones. When I claim that potion, the door appears on my screen. The text from the last part of the tutorial (at least up to this point) gets stuck behind the door itself.
When I move around the UI, nothing is visibly responsive though I can hear the various pips from me hovering over buttons. I can also interact with these buttons (I can see that the bottom third of the wishlist and settings buttons change color when I hover, like the rest is meant to, hence my previous "15/16ths" comment). I can use this to fumble my way back to the main menu where the door disappears and all is normal.
If I try to load that save again, I have the same issue. The UI is being painted over by the door or something? Not sure.
It's also worth noting that I can only see the bottom fraction of the screen when I full screen the game. If I just play through the itch embed on this page then the entire UI is visually unresponsive (though audibly it seems to be fine - like in full screen).
Let me know if you need anything else! Really looking forward to playing this game after the changes you made!