Same issue i have reported has not been addressed.
win10-64bit-radeon-software-adrenalin-2019-edition-19.5.1-may13
win10-64bit-radeon-software-adrenalin-2019-edition-19.5.2-june3
win10-64bit-radeon-software-adrenalin-2019-edition-19.6.1-june7
win10-64bit-radeon-software-adrenalin-2019-edition-19.7.1-july7
All have the same issue. Open your Windows media player to full screen.