In dolphin, if I click “split” to show two different folders and then select a file or folder in one pane and drag it to the other, it crashes. If I instead copy the selected files and then right-click and paste into the other pane, that works.
Opening dolphin from a command line to see the errors, only shows one error:
Well, hard to say with the given information.
I am not aware of a general problem regarding this, at least.
The crash might be caused by Baloo (the file indexer) or the activities plugin though.
Try to disable both, Baloo in “Configure Desktop”->“Desktop Search”, and disable the “File to activity linking plugin” in Dolphin’s settings (“Services”).
Also, are you using the standard packages for kio and dolphin, or are you using additional repos?
Another question: You should actually get a crash dialog, is that not so? If not, it might indicate that your system is not fully up-to-date, this is something that has been fixed in dolphin 15.12.0 available as update for Leap.
So try to run “sudo zypper patch” to make sure there are no updates pending.