I cannot replicate either one of these bugs,
The first one seems to be either a display issue on your end, as it works perfectly fine on my single-screen laptop, or a issue with renpy not loading the code quickly enough, since the sprites and backgrounds are cut and resized on the fly.
Not sure if fullscreen or windowed mode causes it, but do keep me updated on the fix you requested from that other person!
The second one is definitely a bug, but a rather isolated one, for it works fine with my laptop. I suspect it may also be a bug with system locales and it messing up the code/filenames in turn.
If you don't mind sharing, what are the specifications of your system used to play the novel? Thanks in advance