Are you trying to start a profile with the simulators or something else on the same machine or another machine? Any specific drivers ?

Simulators, natively within the Pi. But it also crashed with a custom profile.

Are both of these on a Raspbian system, or is there another OS involved?

I just tried rebuilding again and tried various ways of connecting, starting INDI, and running KStars. I can't get it to crash like you described. I am testing this on the Raspbian computer after running setupAstroRaspbianPi.sh.

I tried starting KStars and running the Simulators profile. I tried starting the INDI Web Manager App and connecting to that from KStars. I tried connecting from my laptop over wifi with KStars o the laptop and INDI running on the Pi. And I tried it with a direct ethernet cable. I can't get it to fail.

This is only on raspbian, as that uses the very latest build, my SM is ok as that just updates from a stable version, I have had it happen before, and when I re built it was fine, but have re built several times now and still the same.
Anyhow I now have the SM running well on the rpi 4 and have managed to configure it to run in 4K with and without a monitor attached over VNC, web based noVNC and Remote Desktop....so will stick with that now..as the lack of 4K was my reason for going back to raspbian...
So all good....

But it would be nice to know what happened

It would, and I intend to find out, all I know is I had the issue before and Jasem sorted it, and all he did was re built it, and I Have tried that four times now...
Others I know have had the same issue yesterday, and rebuilt completely and all is now good...so maybe I will ha e to start from scratch with your script and re build.
It’s annoying as I altered your script to suit my needs and if I do a new git pull, it will undo all the changes I made...
I have been just re building Kstars and INdI, but think will have to do it all again...

I'm on raspbian. Raspberry Pi 4 and relearning how to go about things without PPA.
With that in mind, could I get advice on the steps required to rebuild kstars?
I had a hard time finding instructions on the forum.

You can’t use PPA with raspbian, you Have to build from Source....or use @rlancaste script, it’s excellent...

github.com/rlancaste/AstroPi3

Yes. That was the point, Without PPA, what are the steps necessary to clean/rebuild Kstars from scratch.
Although I ended up just re-running the script, it seems inefficient for rebuilding only KStars. Good news is it resolved the crashing.

All good on my Raspian + pi4B after latest git pull.

Hi guys, is it good to run manjaro arm with kstars and rpi4B? what is the pros and cons if compare with raspbian? Any advice?

Regards,
Tom