Saving existing web maps fails and returns an error in ArcGIS Enterprise Map Viewer Classic

Description

In ArcGIS Enterprise Map Viewer Classic, the attempt to save an existing web map fails and returns one of the following errors, depending on the selected saving option.

The error returned when using the Save option:

Error: 
Your map '<map name>' could not be saved.

The error returned when using the 'Save as' option:

Error: 
Unable to load portal/sharing/rest/content/users/xyzx/addItem status: 500

Cause

Insufficient memory (RAM) or disk space on the ArcGIS Web Adaptor machine.

Solution or Workaround

Note: 
Contact the organization's IT personnel to perform this solution.

Increase the memory (RAM) or disk space on the ArcGIS Web Adaptor machine. Refer to ArcGIS Enterprise: Hardware requirements for more information.