Interesting, I've had mine for a couple of years and there is no film. I'm compulsive about washing it promptly.

This is a polarizing cocktail. I am fine with the strong herbal character but it's a bit much for my wife. No orange juice available, unfortunately, so I added a dash of orange bitters and cut the Fernet to an ounce.
If I try this again I will cut the Fernet in half, and use Antica Formula vermouth instead of the Cocchi Torino. And make sure I have an orange to squeeze.