I’m afraid a lot has been broken in the Plasma desktop environment with this stable update, my friend, courtesy of the upgrade from Plasma 5.24 — which was an LTS release — to 5.25.
The KDE developers have rewritten a lot of the compositing code in order to streamline the code between X11 and Wayland, with the latter being a problem child that has so far required and continues to require heavy adaptations and rewrites to the Plasma code base.
I’ve just written a rant on today’s Stable Update announcement thread that we should have stuck with 5.24 LTS instead of placating the newbies who wanted 5.25 in the Stable branch just for the sake of the version number.
Oh, and… 
I tried that too, and my desktop froze. The panels disappeared and I couldn’t do anything anymore.
Eventually it came back to life, but it did take some time.
5.25 is definitely buggy — that’s a given. 