I can add another case of this happening. I killed all my consoles and now all my attempts to make new consoles come up in Chrome looking like the example picture.
Shift+Referesh didn't seem to help. Nor did closing Chrome completely and restarting.
Tried adding /frame/ to end to make full screen, but that didn't alter either.
Tried closing Chrome and completely shutting down and restarting computer (Windows-based) and still had the issue. While consoles generated in FireFox look normal.
I even uninstalled within Window's Control panel and reinstalled Chrome and it is still doing it.
I cleared the browsing data from the beginning of time with all options on and closed. When I repopen and login to PAW, it still just opens the one line thick black window like in the picture the frst poster, Felix, posted.
SOLVED: Felix's solution did work, but I had to uninstall from 'uninstall' shortcut in Window's Start menu. By doing it that way, I got an option that didn't come up when I uninstalled in Windows list of installed programs in Control Panel. I selected 'yes' to the option to destroy all old browsing data and then reinstallation after that restored my PythonAnywhere windows to be normal in Chrome. What a pain to fix.