When I try to install Software through yast, or run the updates, the process usually starts OK, then midway through the process, it finishes and asks whether I want to add or remove more software. If I say no, the installer closes, and when I try the new software, I find out it hasn’t been installed. If I then restart the install packages via yast (it happens with yast and yast2, through a remote SSH session or not), I have to reselect the software I wanted to install. Some of the software of course has already been installed. If I repeat the procedure it starts installing again, and then suddenly, before it has finished, it asks me again whether I want to install or remove more SW. If I say yes, it goes back to the screen where I can select the software again. As it is still selected, I can use Accept, and the changed packages get listed. I select continue and the installation proceeds. Sometimes it then stops immediately again, sometimes it gets further. Sometimes it even finishes successively after a few retries, but very often it needs a lot of retries, which wastes a lot of time. This has happened on different hardware, so it must be a bug with yast.
I’ve meanwhile managed to finish the updates via yast, but I still get the same issue when installing new packages. So I don’t think zypper up will do anything.
Actually, some users have has similar problems with yast as you’ve described, and the zypper update has helped with upgrading packages including problematic yast package versions. So, I recommend trying it if you still have problems.
Edit: Just read your last post. Were the updates initiated by opensuseupdater with PackageKit backend?