No no, thank you for your help! 
At least we found out, that it is not somehow my device, but the NG image, since the errors with NE and NO do not occur.
I had already posted in the Ugoos X4Q thread:
But nobody has commented on it yet.
Then I went to How to report an issue you’re having with CoreELEC
… create a thread in the appropriate category, describing your issue, how to reproduce it and a debug log.
I thought I was in the right place under Support&Help/Ugoos!
Which thread do you mean, this one?:
What do you mean by “use the support link” and “dmesg”?
It would be a shame, if this couldn’t be dealt with, because otherwise the box works great with the DV support!
But my power supply has a slight beeping noise when it’s inactive (when the device is turned off). For this reason, and because I’m used to it anyway, I would like to always have it unplugged. But that’s not possible.
And I would have liked to have bought the device for someone else and pre-configured it, but when the device does such antics after it has been disconnected from the power supply, it is a bit difficult to explain…
And the fact that you can’t really tell what the operating status is from the device’s LED is also suboptimal.