Thank you very much for your answers and help.
I add a new user environment variable named "QT_ANGLE_PLATFORM" with the value "warp" , then reboot, and I get the same result.
In fact I get the same bug after a while with 0.9.16 and 0.9.15. 0.9.14 is working all fine so I am using it and I am so happy to have it because Sigil is just an amazing tool to edit ebooks.
