Are all of these questions basically asking the same thing but it different ways? The OP has provided their own answer to each, which is exactly the same on all.

https://askubuntu.com/questions/1483993/ubuntu-clock-jumps
https://askubuntu.com/questions/1508292/clock-wont-syncronize-and-drift
https://askubuntu.com/questions/1508554/sudo-timedatectl-timesync-status-has-high-jitter-and-offset
https://askubuntu.com/questions/1508833/marking-clocksource-tsc-early-as-unstable-because-the-skew-is-too-large-and-t