Good news!
Today I had a power failure at home and had to restart my server.
In this context, I have installed updates again, including a new openhab2 snapshot.
And right now I just looked at the display: The entire text has slid up one line and a sixth line has now become visible!
The display seems to work as expected now!
I don’t know if it is because of the new snapshot, or because of the reboot…