Thanks for posting!
We may be dealing with a RF interference issue with the USB receiver for your wireless mouse and keyboard. We have a blog post that speaks to this in more detail if you are interested (https://plugable.com/2017/03/17/troubleshooting-wi-fi-performance-and-wireless-keyboard-mouse-issues-on-usb-docking-stations/).
In summary, this can often be remedied by removing the USB wireless receiver from the front USB 3.0 port and placing the receiver in one of the top-most USB 2.0 ports on the back of the dock. Does this help with the keyboard/mouse issues?
Regarding the monitor issue – I’d like to request some logs from your system to investigate further. Could you please keep the UD-3900 dock connected to your Lenovo laptop (with the displays still attached), then navigate to our PlugDebug tool (https://plugable.com/support/plugdebug) and follow the instructions there?
This will create a ZIP file on your Desktop containing system logs and information. Please send that file to us directly at firstname.lastname@example.org with the subject line “Ticket #259201”.
Thanks for giving us a chance to help!