I’m experiencing the same problem described by jwb in July 2019 with an intermittent signal loss between a Plugable UD-ULTCGL USB-C Triple Display Docking Station and a Dell U3818DW. I just bought the Plugable USB-C Triple Display Docking Station this past week (May 2021) to connect to my Microsoft Service Book 2.
Has Plugable has updated the product to support 3840 x 1600 resolution yet? If not, does Plugable make a docking station that supports 3840 x 1600 resolution?
Dumbing down the resolution from the recommended 3840 X 1600 to 1920 x 1080 is like connecting to a cathode ray tube (CRT) salvaged from an electronics landfill.