Trying out the source, opening the project in Unity 2021.1.10 (which gives of course a warning that it's updating the project from 2021.1.7). Loads of errors because it wants to run Blender which I don't have installed (yet, will fix this in a moment). Lot's of warnings about assets that have not their corresponding meta files with them.
One warning about Dialogue.cs line 85 which has an assignment in an if() expression which is likely a typo meant to be a comparison ('==' instead of '=').
So maybe it's running off the end of the intro message and therefore throwing an exception and resetting to the beginning of the message? Will check this out...