If you have the Technician Auto Assign enabled(Admin-> Technician Auto Assign) please configure it to apply only for unassigned requests. Additionally we request you to check under Admin-> Helpdesk Customizer-> Category to make sure that the Technician assignment does not happen based on the Categories.
If the issue persists, please create the Support Files and send it to support@servicedeskplus.com referring this forum post. The Support Files can be created under the Support tab.