I found out that when not zoomed in (i.e. working with an image full schreen) in 16 bits mode, the image that you see is calculated in 8 bits mode (to sav processor loading).
This means that what you see is not nesessarily the correct image.
(see the follwing discussion for an expanation and example)
https://community.adobe.com/t5/photoshop-ecosystem-discussions/what-you-see-is-not-what-you-get-imag...
It would be great to have the option in settings to force Photoshop to always show the 16 bit image even when zoomed out. It is then up to the user to judge if he wants to opt in and risk a slower response.