I can't reproduce this on my Arch-based system. That warning at the end there shouldn't have anything to do with file saving or exporting, but I did fix it recently, as well as changing how the desktop resolution is detected on Linux so that it doesn't launch (since a recent SDL2 update, maybe?) as a tiny 128x128 window in this commit a few days ago: https://heptapod.host/jp-lebreton/playscii/-/commit/a1e0fae59d0a8c06d045709da109...
If you're running from source you should be able to download the version of playscii.py there on the code repo and just replace your local file with it. But like I said, I'm guessing those fixes are unrelated to the problem you're seeing.
Two questions that might be relevant:
- Does your home directory have a Documents/ folder?
- What distro are you running?