Please start a gdb console for the last crash with coredumpctl debug kwin_wayland, get a backtrace in there with "bt full" and create a bug report with the backtrace at bugs.kde.org

Are you using a distro with fairly recent packages? If not, then possibly you could try looking for supplementary sources that could provide more recent version. Just as an example, someone else mentioned having a similar issue on Debian. Debian tends to be very conservative about updating their packages and they may be quite outdated. (It's possible to be on the other side of the problem, with fast moving distros like Arch but they also tend to fix stuff pretty fast as well.)

Possibly worth considering that hardware can also cause random crashes, faulty RAM, overheating GPUs, CPUs, memory or overclocking stuff beyond its limits. Try checking sensors to make sure temperatures are in a reasonable range, etc.

You can also try to determine if the times it crashes have anything in common or anything unusual is happening. I.E. playing graphics intensive games, hardware video decoding, that kind of thing. Some distros have out of memory process killers set up that have been known to be too aggressive, and processes like the WM that can control a lot of memory will sometimes be a juicy target for them.

As you probably already know if you've been using Linux for a while, diagnosing problems is usually a process of elimination. So you need to eliminate as many other possibilities as you can. Also, it's general hard for people to help you with such limited information. We don't know the specific CPU, GPU, distribution, versions of software, what you were doing when it occurred, anything like that. So we can't eliminate many possibilities to give you more specific help. More information is almost always better when asking for technical help on the internet.