I was using my Pi with KStars 3.0.0 two days ago and it worked like a charm. Yesterday however I had a strange bug.
So I did everything exactly as I did it two days ago. After platesolving and ready to start capturing, I wanted to change the name of the object I was about to capture (prefix) in the camera tab.
There was already "star" filled in, as I solved on a star. As soon as I clicked in the field, the EKOS window disappeared. It was just gone.
Even more stranger, tracking and guiding was still working! So I tried to start indi again, but it told me that another instance was already running.
I couldn't get back to the EKOS window, so i rebooted the Pi and tried it again, with exactly the same result.
I attached the 3 log files for you, hope it helps.
Before the window disappears, it always says the following in the log files:
[2019-02-27T20:28:21.617 CET WARN ][default] - QWidget::paintEngine: Should no longer be called
[2019-02-27T20:28:21.618 CET WARN ][default] - QPainter::begin: Paint device returned engine == 0, type: 1