the game isn't bugging at all, I played through it with the walkthrough mod, and just recently your mod and it played 100% no issues. On mac
What i'm saying is there is a slight problem when following the directions exactly as posted for Mac. When you copy the game folder and overwrite it, it overwrites the ENTIRE folder. You only need to copy the files from your mod folder into the WTHI game folder.
Here is some screen shots of what I mean
Original game folder
View attachment 616018
Game folder when you do exactly what the instructions say
View attachment 616019
You only need to copy the files and not the whole folder, as when you do try to copy the whole folder this is what you see
View attachment 616020
When you hit replace it replaces the whole folder and not just the files.
I'm pretty positive that is what is causing the errors. That's what happened to me when I first installed the mod.