Symptoms

Tried to reinstall K2 SharePoint components on SP 2010, but there are WSP files deployment errors. 
 

Diagnoses

Legacy .dll files from a 4.6.11 install were preventing the deployment of new .dll files to the Global Assembly Cache (GAC) in the Web Front End (WFE) servers when the customer attempted to uninstall 4.6.11 and reinstall 4.6.3 in their Staging environment.
 

Resolution

Attempted to uninstall the assembly files manually from the GAC. When this failed, we attempted to delete the registry keys to force the uninstall. This also failed.

Next the Microsoft gacutil.exe was run to remove the assembly files from the servers where errors were reported during the deployment of K2 for SharePoint. This had to be done numerous times, as each time the K2 for SharePoint deployment was run new .dll's were reported as being unable to copy to the server.

Once all components of K2 for SharePoint were deployed, http 503 errors were now being seen on the WFE servers. An IIS reset was conducted, However the SharePoint services had to be started manually in the App Pool. After it was verified that the customer could reach the WFE servers and the K2 components were functioning correctly.