Remember Master Password on This Device Does Not Work (Since Several Months)

My master password is around 30 characters, and not fun to type on mobile. Because of that I’d rather rely on iPhone passcode and let Key remember the master password. Since Nov-Dec last year it hasn’t worked. If I tap in the password and enable ”remember” setting, and swap between two apps, key asks for the password again. Immediately. If I kill Key by double tapping home, and by sswiping up, it doesn’t ask the password when it’s restarted. But immediately if I jump between apps, it prompts for password again. SAD! As DJT would say.

iPhone 5, latest iOS.