Attempting to assign a new snapshot to a VMware Horizon View 5.3 pool throws the error: “Server Error” with “Unknown” description after upgrading to Horizon View 5.3

I ran into an interesting problem the other day while trying to assign an updated snapshot to a linked clone pool after upgrading an environment from VMware View 5.1.2 to VMware Horizon View 5.3 where I would receive the following error after assigning the new snapshot:

… then clicking on the OK button:

Server Error

Unknown

What was strange was that out of the 8 linked clone pools, 5 would complete successfully while the other 3 wouldn’t.  Logs in the DriveLetter:ProgramData\VMware\VDM\logs folder on the View Connection server and the Composer logs on the vCenter where the service was installed did not contain any errors either.

After restarting the Composer service without any luck, I realized that the View Administrator GUI I’ve been looking at did not appear to be the Horizon View theme with the blue background so I went ahead and closed the browser, then relaunched it to log back in.  Upon landing onto the login page, I immediately noticed that the theme was now Horizon View 5.3 with the blue background so I proceeded to log in and was then able to assign the new snapshots to the 3 problematic pools:

I’m not exactly sure how this happened as this couldn’t have been a situation where I updated the View Connection server without re-logging back in as my session would have been invalid after an upgrade.  Since searching for the string above did not return any useful results, I hope this post would be able to help anyone who may come across the same behavior during or after an upgrade.