S5 required to enter Google pw for factory reset. Only allowing me to input 15 characters. Pw is 32 char
If you are sure it's asking for Google password, then you can change your Google password online for now to something shorter.

But, i believe that it doesn't ask for Google password, rather it wants your lock screen password or a special password, that you have set up under settings>security>factory reset data password.

Another option is to do a factory reset using hard keys but if you do decide to go with that option, then don't change your Google password before doing it, otherwise you might be locked out of your device.