

I have no idea what you’re doing wrong, but I’ve been using Debian for over twenty years and it’s by far the most stable OS I’ve ever used, particularly the update system. I’m currently maintaining around 50 debian systems and never seen an issue you like you’ve posted, so no, there’s nothing average about what your’e saying.
Has it added repos that are conflicting with your distro’s main ones?
Check /etc/apt/sources.list and all the files in /etc/apt/sources.list.d/
Move anything that looks sus to somewhere else and then “apt-get clean” and retry.