Ended up posting this to the forums of the dock manufacturer
https://support.plugable.com/t/ubunt...e-issues/19238 where they suggested trying newer NVidia drivers or reverting to Ubuntu 18.04.
Neither worked but I'm pretty sure I've narrowed the problem to actually being a problem with the NVidia driver as disabling that GPU and using the integrated graphics in conjunction with the DisplayLink connected side monitors seemed to work just fine.
See the other posting for a far more detailed description.