The Apex object cannot be serialized. The VFJSRemotingEnforcePref value is ‘true’

Error: “The concrete implementation ‘rsdoc.DocumentManager.GenerateResult’ in namespace ‘rsdoc’ has a JsonAccess annotation serializable attribute defined that prevents serialization. The Apex object cannot be serialized. The VFJSRemotingEnforcePref value is ‘true'”

This error occurs when an Opero Documents customer enables the Salesforce update “Enable JsonAccess Annotation Validation for the Visualforce JavaScript Remoting API” with a package version of Opero Documents that is older than 2.143. Customers must update to Opero Documents package 2.143 or greater before they enable the Salesforce Enable JsonAccess Annotation Validation update, otherwise it will break document generation.

Salesforce made this update available in the Winter ’23 release. It will be enforced in the Salesforce Winter ’24 release. If Opero Documents customers do not update the package to 2.143 or greater before the Salesforce Winter ’24 release date, it will break document generation.