Thank you for posting! I am sorry things are not working as expected while using your UD-3900 docking station and I would be happy to help.
Thank you as well for the detail you provided and the troubleshooting you have already performed that is much appreciated.
You mention that, “Monitors freeze (clock displayed on screen saver stops), and the only option is to do a hard shutdown.” When you say ‘monitors’, does that include the Surface laptop’s built-in internal display (assuming that the laptop lid is open while docked)?
Apologies if the question appears in any way redundant, however I just want to ensure I have the details correct and not make any incorrect assumptions.
That said, the behavior you describe is not typical or expected so our next step is to get some additional information.
If you would, just after the behavior has occurred again and the system has been reset please keep everything connected and send the output of our diagnostic utility PlugDebug --> http://plugable.com/support/plugdebug to us directly via email@example.com with ‘For ticket #- 302473’ in the subject line. This will allow us to match things up as well as examine some log files from your system to help determine the next steps.
** Please also include the Amazon Order ID number for the UD-3900 purchase in your direct email, it is required to confirm warranty status **
** Please do not post the PlugDebug file or the Amazon Order ID number in our public forum **
Apologies again for the frustration, and thank you for giving us the chance to help!