Hello, Unfortunately there were a few packages of Xfce 4.18 that recently made into X11:xfce and Factory, causing a partial upgrade. Nothing seems to have broken so far and we will send the remaining packages asap. If you notice issues please do report them, and if necessary we may consider reverting back to 4.16.
Xfce 4.18 is currently being packaged and staged in https://build.opensuse.org/package/show/X11:xfce:next/. If you wish to contribute to the upgrade effort, it is very much appreciated, and you can send SRs there instead of X11:xfce.