Is your password manger able to limit length. The Tips on Tueday #2 says passwords must be between 8 and 16 characters. Also recommends using the mobile app to change.
https://www.youtube.com/watch?v=lQSf1ce7m-M
Also, it almost sounds like your password manager is out of sync on the two devices. In other words the device is remembering the last password it used to change the password.
You may want to change on the Mobile App, then close your broswer on the PC, and reopen so the password manager is forced to get updated copy.
Just guessing…