Well, I don't use the synaptic package manager nor discover. I go with, and this is recommended on unstable/sid, apt update; apt full-upgrade: and all while logt in graphical, on the desktop (kde/plasma/kf5).
I did not run in problems for a long time.
Why not using that graphical tools?
Because this is debian unstable, and they are made for a stable distribution because of handling the problem solver, it works much better with a command line tools like apt!
With synaptic or discover you will run into problems, sooner or later.
You can use them for searching a program, but install it with apt!