can't boot on win10 without alt (option) on an air macbook air 2017, I deleted OSX and installed only Windows 10 from a usb cd drive. Everytime I boot the computer, I have to push on ALT to select the only one item: Windows. Otherwise I get a blackscreen with a folder and a question mark.

When windows is loaded, under control pannel>bootcamp, the startup disk is: "Basic data partition Windows" and this is the only one available

What can I do to fix this issue ?
I don't know what happens but the issue is solved after a lot of reboot