If you remote desktop into Ubuntu 16.04 you may have found that recently you are unable to do so with a misleading “password failed” message. In fact, if you actually got the password wrong it would say “login failed” earlier in the process.
E.g. when logging into sesman-Xvnc you see
security level is 2 (1=none, 2=standard)
error - problem connecting
This came about as a security update, is a known bug (https://bugs.launchpad.net/ubuntu/+source/xrdp/+bug/1811122)
and downgrading currently works as a workaround:
sudo apt-get install xrdp=0.6.1-2