Try connecting a secondary power source to the MBP (power brick using USB-C, etc.) and see if you still have connection issues or if it stabilizes. I went through three TS3+ docks, before I seemed to get a good one. For the problematic ones, connecting a secondary power source seemed to fix things while I waited for the dock replacement. At least for the issues I was seeing (dock disconnecting/reconnecting on its own) while connected to either 2016 15" MBP or 2018 15" MBP. For my problematic docks, I think it was primarily related to power delivery to both the MBP and any USB devices that required higher power, in my case, a Yeti microphone and/or an external 2.5" hard drive. Though I will say my current primary monitor does deliver up to 94W PD over TB3, but is connected directly to the dock.