Thanks for playing! That error might be because of a re-loading issue, as I've never encountered it during my testing, though I'm not surprised it happened: MZ3D is notoriously bad at parsing issues with its interaction with RPGMaker, so it often responds by crashing the whole thing. I actually avoided using skyboxes this time around just to lessen the chances of that happening!
I should be able to fix it by adding a clause that the player is "locked" into place while talking though, and I'll be fixing whatever else I can until then too. If you ever feel like attempting the game again, you can reload from the autosave (or your own manual save if you did one), and skip to level 19 using the Level skip trick (Hold Z and X while accessing the options menu in-game).