I'm not completely sure but I'm also having this issue. The funny thing is that this error was not being thrown by the Log a few hours ago. What I can tell you from my experience is that it seems like my WC admin password it's (somehow) being changed and I got this error when I started to experience this random password changes.
Maybe you can take a look at your ptc-windchill-integration-connector and change the password (probably is not set correctly for the user that you have there). In my case is my Windchill Administrator user.
Let me know if you found anything different on your side.