A bit more info for future readers:
There is a bug in V25.20.14146.3004 of AMD chipset driver (the latest version available in the Asus UM462DA support page) which causes videos to start with a green flash. I happened to uninstall this version and let Windows auto install 26.20.12028.2 which solved the bug.
I've also did an update to 27.20.12027.1001 (Adrenalin 2020 Edition 20.8.3 Optional on AMD's website) which seems to be better in thermals than 26.20.12028.2. I am not sure about this, still.
TLDR: the newest chipset driver on the Asus UM462DA drivers page (
www.asus. com/2-in-1-PCs/ASUS-ZenBook-Flip-14-UM462DA/HelpDesk_Download/) has a bug which causes a green flash to appear whenever some videos are played. The solution for me was to install a newer version of the driver.