Update of 28/02/2019 disturbed by the resolution of the screen

I have just updated my system and the resolution of my external display is disrupted. Instead of the usual 4k (3840×2160), the maximum I can set with the GUI is 1680×1050.

Everything worked well before this update.

I've already tried this solution and I can see the 3840×2160 option in the View menu but that does not change the screen resolution.

Thanks for the help,
Pierre