I encountered the same symptoms on my system. On CentOS 7.7, when starting tigervnc server service I was getting the following error message:
# systemctl start vncserver@:1
Job for vncserver@:1.service failed because a configured resource limit was exceeded. See "systemctl status vncserver@:1.service" and "journalctl -xe" for details.
(but vnc server actually worked without issues). The error message was caused by the recent updates to systemd in CentOS 7.7:
I tried to follow the workaround instructions (in the link above) by changing
-u and removing
/etc/systemd/system/vncserver@\:1.service file. This eliminated the systemd error message but created the issue described in this question: the user password field in the VNC client window was reset/refreshed so frequently that there was no way to login into the machine!
Changing things back in
/etc/systemd/system/vncserver@\:1.service solved the issue with the screen refresh. So, my suggestion would be to ensure that you start vncserver with
runuser -l <user> -c .... Seems like some environment variable might not get reset if
-l is not used and this manifests in the frequent screen refresh...
Hope this is helpful...