Okay. So reverting back to the old_twilight_knight files and the 217 error message is back.
I managed to find an old archive folder containing old versions of the atlas & skel files so I used them. The 217 error went away but the 179 remained. The main difference between these old files and the new ones is file size. I notice that in the new batch, for some reason, twilight_knight.walk.skel is a 0 kb file size. The leper’s walk skel is 45.8kb, the old TK one is 46kb (the class name probably makes up the difference with a few extra letters) and yet the new Tk walk skel is a 0 kb size file.
The walk skel seems to be related to the 217 error. I haven’t managed to nail down the 179 error yet but I’ll keep on looking.