Client does not accept complex passwords

[HM9cPhABFctJ]

WoW Freakz link: n/a
Bug description: After registering and downloading the full client (Torrent) I attempted to login, following the guidelines outlined on this page: https://forum.wow-freakz.com/WoW-Legion-client-t452441.html
I was then presented with "We couldn't log you in with what you just entered. Please try again. (BLZ51900003)". None of the listed solutions worked. Being familiar with the official client and Battle.net's flaws in password validity I then assumed it was a problem there, so I simplified the password (was 16 characters, completely random, including symbols. Reduced that to 12 characters, alphanumeric, no symbols). That worked.

Might want to list that as a possible solution.

Also note that the original complex password worked fine on your website, it is just the client that did not accept it. Which is probably Blizzard's fault. As stated, even the official client and Battle.net service have issues with complex passwords. I have reported this a few times over the years, nothing ever came of that.
Proof: n/a