Upgrading Orchestrator From 2018.4 to 2020.10

Observed Behavior

After upgrading a LongPolling disabled Orchestrator from 2018.4 to 2020.10, the 2018.4.6 Robot remains connected and consumed ports and fails to execute a job.

The error message displayed is Insufficient memory to continue the execution of the program.

Full error message:

HubConnection start failed, err : StatusCode: 400, ReasonPhrase: 'Bad Request', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
HubConnection start failed, err : An error occurred while sending the request.
HubConnection start failed, err : An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full
System.OutOfMemoryException: Insufficient memory to continue the execution of the program.HubConnection start failed, err : StatusCode: 400, ReasonPhrase: 'Bad Request', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
HubConnection start failed, err : An error occurred while sending the request.
HubConnection start failed, err : An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full
System.OutOfMemoryException: Insufficient memory to continue the execution of the program.