I’m not sure which recent update/upgrade cycle introduced this issue. I tried a further upgrade tonight 16 August 20:00 UTC and the crash issue is still happening. KStars goes back to earlier settings when it restarts.
I found a simple workaround to keep the old settings in KStars and close it down cleanly is to Disconnect each item of 'my astro gear' on the Indi Control Panel and then stop the Indiserver. Closing down KStars then keeps settings intact.
I can confirm the issue. KStars crashes when I press the "Disconnect" button (under "3. Connect & Disconnect Devices"). It does NOT happen with simulators. Also, it does NOT happen if I disconnect devices one by one in the Indi panel.