Photo link [URL] Let's just resolve current issue.  WD19TB (old) + WD22TB4 Module (new) (No output to any monitor except laptop itself screen) I don't have WD22TB4 dock but just its module. 
I plugged in the newly purchased "WD22TB4 Module" to my existing "Dell Thunderbolt Dock - WD19TB", the dock does not show anything on my monitor. And then I have to swap back the existing module to get it work.   Not sure my new module has issue or they are not actually compatible.  My laptop: Precision 5750      
new WD22TB4 Module does not work with my existing WD19TB Dock