Can't change password via web page profile

try to change my very old password (not changed in the last 5 years) via webpage https://www.minecraft.net/de-de/profile

I enter my old password and the new one (requirements are all matched).

After clicking "Change Password" I get the following message.

"Password too weak"

Same happens when I try to reset the password via e-mail. Then the message appears that "Something went wrong".