BDP-320 output frequency 50-60 Hz

[Yodo]

My TV can only understand the 60 Hz frequency (NTSC).
When playing US DVDs there is no problem.

However, playing a European DVD at 50Hz gives a TV black screen (bad frequency).

It seems there is a remedy in the manual (p. 22, "About the frame/field frequency and NTSC/PAL TV systems"). It says:
- Eject the disk
- Press Open/close while pressing Play

=> that switches the frequency.

That's correct. The frequency on the LCD panel changes from 50 to 60 Hz.

However, as soon as the disk starts to be loaded, the freq goes back to 50 Hz... and remains like that.

Is it a bug of the player? Or my understanding of the "remedy" is wrong?
Is there another solution?

[using the latest firmware 3.65]