So I reset my forgotten password with this method and now cannot set a new password. Every time I get

> The password you entered to protect your iPhone backup could not be set. Please try again.

What happens then is: the password i set is actually active, becuse to back up i have to enter that password - but as soon as i unplug the iPhone and plug it back in, I can/have to set e new password.

I updated iTunes to the newest version, restarted the iPhone, reset the iPhone settings multiple times, but I cannot encrypt the backup anymore. Weird.

edit: (the solutions to this problem that google offers did not solve the problem)