The problem we have is the build tool was (it seems) updated to ignore the key password when creating keystores. So people kept entering a key password when creating a keystore, which was ignored, then re-entered it when signing the app, and then getting "wrong password" errors. This change was in the beta release for about a month before it came to a stable release, which gave the impression the change was OK.
If we add back a key password field just for signing, we'll be asking people to enter a password they never previously specified, which would probably cause further confusion.
So it's not clear to me what to do here, it seems this change to the build tool has thrown a spanner in the works. AFAIK whether or not you can change the keystore depends on the precise method you use for publishing, and in some cases I think you can change it. Otherwise you can try downloading the Java keytool and changing the key password on the keystore - it needs to match the keystore password, since the build tool now only supports both the keystore and key passwords being the same.