After some further digging I figured out the problem but it makes zero sense. A)  Found this article about resetting the docking station but it provided zero help. [URL] I was stumbling around some other forums and someone suggested disconnecting the monitors from the docking station before doing the firmware upgrade and that fixed the problem???  This makes zero sense.  I was able to upgrade (3) different docking stations with zero problems.  If someone can explain why this worked, it would be greatly appreciated.
We mostly have WD19TBS docking stations in our environment and a handful of WD19TB docking stations.  Were using Windows 10 Enterprise 64 bit as our OS and we can't get any of our WD19TBS docking stations firmware to upgrade MST from version 5.04.06 to 5.06.03.  It just fails every time.  Were on the current version of BIOS (Version 1.18.2) on a Latitude 5420.  The update is being run in an admin account.  I've also tried to run the executable in Windows 8 compatibility mode with no luck.  I've upgraded every driver on the laptop that can be upgraded but still no luck. I thought I had stumbled upon a forum that the docking station firmware can only be upgraded using Windows 10 Pro 64 bit and that doesn't sound right because their has to be thousand of companies using Windows 10 Enterprise that need to upgrade the docking station firmware in order to fix bugs. Any ideas because I've run out of everything to try?? Note:  Were able to run the firmware update successfully on some of the WD19TB docking stations which doesn't make sense.       
Docking Station Firmware Update Failure