Thanks all for the replies and explanations!
Did you change to interleaved loading mode (LoaderMode 1 in the main.cfg file)? If not, try that and see if anything improves.
I didn't change anything, but I found it to be set to 2...
It is really sad, I got somehow fond to that place... A living planet with a bright day and a pale blue night... Fortunately I did a video and a couple of pictures, which I'll post in the right section and title them "The lost planet" or something different not to infringe any copyright.
P.S.: This is my second post here and just wanted to say that SpaceEngine is really a great piece of software. Since I discovered it, I fell in love with it! Keep on the good work!!!