@rfedorchuk You can follow the below steps.

1. Create a resource using Resource Management > Resource > New Resource Group. Resource Type = Person Group and make sure to toggle-on User IN Maintenance under Resource Usage. 
2. Get the created resource id in Resource Management > Resource > Resource Details, then add the person to the person tab.
3. Select the relevant person from the navigator
4. Add the employee in the Employee tab
5. Add the Maintenance Org in the Site Settings.

This is where we are seeing the error appear.  

Everything works fine until here: