Monitor Model# Dell 24 ICM Monitor - P2418HZmDocking Station Model# Dell Thunderbolt Dock- WD19TB Solution / Work around#It can be resolved by using the docking station port "9. Thunderbolt 3" as labeled in the instruction manual and with the purchase of an adapter from amazon i.e. "Amazon Basics USB-C3.1 Gen1 to USB-A Adapter with Data Transfer up to 5Gbps (USB-IF Certified)" and then connect the 2418HZM USB hub cable from monitor to the adapter. Additionally download and install all the latest drivers for the dock from Dell portal.
The webcam in my Dell P2418HZM monitor with integrated video conferencing capabilities will stop working when on a Zoom or Webex video conference after several minutes when the monitor is connected to the Dell WD19TB docking station.  I am running a Dell Latitude 7320 laptop running Windows 10. I also have a Dell U2720QM monitor connected to the WD19TB docking station.  The webcam in the P2418HZM monitor works fine nitially but after several minutes the webcam freezes. There is no impact to the speakers, microphone or video display on the monitor. It only appears to be the webcam that stops working.  Everything works fine when the P2418HZM monitor is directly connected to the Dell Latitude 7320 laptop. 
P2418HZM webcam stops working with WD19TB docking station