Running kf5 / plasma5 from kf5 stable repo. I reported this upstream to KDE
team and they could not reproduce it.
(https://bugs.kde.org/show_bug.cgi?id=345381)

I have a Folder widget on my desktop. It shows the Desktop folder. I have a pls
file there , call it music.pls. If I right click music.pls and click 'Open with
-> VLC media player', my entire plasma shell / desktop is frozen. Can't
interact with the menu, panel, widgets, anything.

VLC runs and plays the music fine, but when I close VLC, then I get an error
dialog "Sorry - Plasma", "KDEInit could not launch
'/usr/lib64/libexec/kf5/kioexec'" "OK". When I click OK, my desktop returns to
normal and I can interact and click stuff again.

This only happens with Folder widget. If I repeat these steps from a Dolphin
window, there is no problem.