Repeatedly prompted to change password on every ssh login

I have a VPS with Ubuntu 18.04 on it.

On every successful login with user root, i get prompted:

Changing password for root.
(current) UNIX password: 
Enter new UNIX password: 
Retype new UNIX password: 
root@ubuntu...*:~#

When I check the expiration date of the password:

root@ubuntu...*:~# chage -l root
Last password change                    : Jan 30, 2019
Password expires                    : never
Password inactive                   : never
Account expires                     : never
Minimum number of days between password change      : 0
Maximum number of days between password change      : 14600
Number of days of warning before password expires   : 14

What is wrong? I want to choose a permanent password.

Oops moment.

The reason for this is another multiplexed SSH session open for all this time. After closing it, the password reset requests stopped.