I figured it out...I had set my body size to 700x700 (which is what I originally exported my png as) but the "size and position" animations for the body when talking and screaming were set to size 600x600. I think it was applying the size change even though I had no animation selected specifically on the body and even had the "size and position" box unchecked. Maybe a bug? I ended up re exporting my png at 600x600 because it was easier than resizing all the pieces everywhere in the app. Suggestion: in a future release add a way to change the "default" size that gets applied everywhere.
Other feedback:
I have been seeing the same "The system cannot find the path specified: 'Assets'" error that other commenters have mentioned. When I went to the "%AppData%\PyNGtuber\Data" folder in file explorer, the Assets folder was there. I was worried about removing it entirely because I didn't want to lose the work I had already done on my model. However, I waited a few minutes and opened the program again, and it magically worked. I've replicated the open program > see error > close and wait > open program > it works flow multiple times over a few days. Without fully debugging it, my best guess is that a background process could be "using" that folder (like microsoft onedrive or a virus scanner) and preventing pyngtuber from accessing it temporarily.
I am also seeing the occasional lag between the app and obs, same as other commenters mentioned.
I love the ability to bind toggles to key combinations! One of the main reasons I wanted to switch png apps is because the one I was using wouldn't let you set toggles to multiple keys, so I would be changing my expression when typing, using in game key shortcuts, etc.
I'm excited to see how this app evolves and what features you add!