OS glitches out when 0B of space is left

[kaixoo12]

Hi, I'm having a semi-serious issue with my computer and I don't know if I should report it in Github or what

My computer was working fine until I noticed

1. I can't login into any user when using Wayland (I go to a black screen with a blinking and then back to the user switch screen)
2. When I go into user "programar", the background image is blinking between dark mode on and off (but the rest of the system isn't) and I get a warning "no space left in system root". Also applications take long to start and seem bugged-out
3. However, when I login to the admin user using the X11 session, and check the drive space in the file explorer, I find "21GB free"

I think this is a generic Linux thing rather than elementary, but maybe we should avoid all these symptoms:

By warning the user before the disk is 100% full and they can't enter into the system.
(I'm not entirely sure the issue is due to a full disk, because the file explorer says 21GB are still unoccupied)

I removed some files and the issues seems to have gone away, but maybe this should be reported on Github?