7.1.1 "set to default app " option is missing

Impossible to set a music player ....this option is no longer available , under players list ....as it was before the recent update

Now i have noticed , in settings where i can set web browser and the app for it ....action " open media file " is missing ....just dosent exists , witch i believe is the reason of the problem ....each time i open an mp3 file in my file manager , it shows me the list with players ....but the bar with "set as default" is just blank ....anyone can help with that issue ?

When you get a list of players to open the mp3 file with, there should be choices of Always and Just this time. Always sets the app you choose as the default. Juwst this time doesn't set any default. Use Default App Manager to make it easier.