Gnome is currently the least stable major desktop. By far. It's an absolute disaster crippled by tons of little bugs that creep in when you least expect them. Even if you don't add anything to it and use Gnome as vanilla as you can get it, it's still going to be problematic.
Plasma has some small bugs here and there -- and there was a point a few years ago when Plasma seemed like they didn't care about bugs and instead just threw out a ton of shiny new pointless features every release instead -- but recently it is incredibly solid in general and more usable than anything else in Linux, by far. One of the only things I find "buggy" about Plasma is when someone tries to over-rice the desktop with tons of widgets and other things everywhere.