Unable to modify a provisioning template with many Host Group combinations in Red Hat Satellite 6

Issue

• When trying to modify a Provisioning Template, it throws below error after clicking submit.
• When trying to add Smart class parameters, it throws below error after clicking submit.

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator at [no address given] to inform them of the time this error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.