Here's what it shows to me when the message with faces appeas, alongside the crash. For context, I did updated the EliMZ Book, and FaceWindow is placed under it. Hope the developer can resolve it soon! The link to image is below, because itch io disallows posting large images.
https://ibb.co/jkTJ4wMg

Hi there!

Thanks for the report. I will only be able to fix this later tonight.

But for now, you can replace the "ImageManager.getFaceSize()" with 144. Or the number you set to the face image on the database.

Oh, in fact, I think you may need to update your RPG Maker MZ Core codes. Open the editor > Game > Update Corescript

I did, and once I also updated the Fossil, it seems to work just fine now. Thanks!

Have fun!