Author here. The last time I used KDE was during the 4.x days. I remember trying multiple versions, from the earlier 4.0/4.2 days until something like 4.14. Even so, I kept getting crashes and instability.

I remember the one that finally made me stop using KDE altogether and migrate to Gnome 3 at the time was one crash that I would get frequently with Dolphin while randomly browsing fils (that would stop once I removed all Dolphin configuration files but go back after a few weeks).