character encoding changed?

iOS 10 and iOS 11 won't accept my iTunes Backup Password which was accepted by earlier versions.

Typo excluded since the password has been generated and stored in my password manager and I use copy & paste to enter it in iTunes.

The password contains the character backslash ("\").

Question #1: Is the encoding of the character backslash in recent iOS versions different from its encoding in earlier iOS versions (considering the locale German)?

The locale of my iPhone 6 and of my Windows 10 PC running iTunes (current release) is German.

If answer is YES, Question #2:

How to achieve the former encoding of the character backslash while entering the iTunes Backup Password?

Thanks in advance for your help.

Ernst