First, Philips suggested:
Can you please upgrade the 43BDL4050D with the latest released FW :
Scaler 1.102 and
latest released android
That didn't solve the problem.
Then Philips sendt me a newer version:
Android firmware, version 8.06
Now I have the option to choose text size to "Normal". That solved the problem. Xibo works well now.
It's a shame that Philips had removed the "Text size option" in earlier firmwares.
Anyways: Xibo works and I am happy now!
See Attached image where I choose text size: