Okay, I'm not sure if this is where this goes, but it's my best guess. Anyhow, here goes. This morning I had a rather interesting experience with KDE 5.8. For about 3 hours my internet connection was partially down (ie, I could move data, but had no dns) and during that time systray kept crashing. Not the whole thing. Just half of it. The icons would just go away in the panel, and when you hit the little arrow to view the options available, only half the normal apps that you'd see in there were present. Even in settings they were gone. So I did a log out/in to refresh it and it'd be fine for a while, then it'd crash again. So I rebooted. Same odd behavior. IE, it'd be fine for a bit, and then it'd just go away with no warning, error or explanation. However, when DNS resolution was restored, the problem went away. Again, I'm not sure if it's an actual bug or not, but I just wanted to throw that out there in case it was. Like I said, it was flakey all morning until the dns issue resolved itself and now everything is playing nice again.

I am having a similar issue. My wifi is already a bit buggy - it disconnects/crashes at random. Usually removing and plugging in the dongle works. But on KDE, and only on KDE, do I have to reboot my computer. It says it's connected but I can't go to any website.

Yeah, with mine it just seems to crash the systray whenever the network isn't working right. Sometimes it crashes a whole lot more than just that. However, the systray is the only thing that does that consistently. The others seem random.