Sigo recibiendo unmax recursion error con esta consulta.

l principio, pensé que era porque se estaba devolviendo un valor nulo y luego intentaría hacer coincidir los valores nulos que causaban el error, sin embargo, reescribí mi consulta para que no se devuelvan los valores nulos y el error aún ocurra.

Cuál sería la mejor manera de reescribir esta función, para que no se produzca el error?

WITH EmployeeTree AS
(
    SELECT 
        EMP_SRC_ID_NR Id, USR_ACV_DIR_ID_TE Uuid, 
        CASE Employees.APV_MGR_EMP_ID 
           WHEN Null THEN '0' 
           ELSE Employees.APV_MGR_EMP_ID 
        END as  ApprovalManagerId 
    FROM 
        dbo.[tEmployees] as Employees WITH (NOLOCK)
    WHERE 
        APV_MGR_EMP_ID = @Id 
        and Employees.APV_MGR_EMP_ID is not null 
        and Employees.EMP_SRC_ID_NR is not null  

    UNION ALL

    SELECT 
        EMP_SRC_ID_NR Id, USR_ACV_DIR_ID_TE Uuid, 
        CASE Employees.UPS_ACP_EMP_NR 
           WHEN Null THEN '1' 
           ELSE Employees.UPS_ACP_EMP_NR 
        END as ApprovalManagerId 
    FROM 
        dbo.[tEmployees] as Employees WITH (NOLOCK)
    WHERE 
        UPS_ACP_EMP_NR = @Id 
        and Employees.APV_MGR_EMP_ID is not null 
        and Employees.EMP_SRC_ID_NR is not null  

    UNION ALL

    SELECT 
        Employees.EMP_SRC_ID_NR, Employees.USR_ACV_DIR_ID_TE, 
        CASE Employees.APV_MGR_EMP_ID 
            WHEN Null THEN '2' 
            ELSE Employees.APV_MGR_EMP_ID 
        END  
    FROM 
        dbo.[tEmployees] as Employees WITH (NOLOCK)
    JOIN 
        EmployeeTree ON Employees.APV_MGR_EMP_ID = EmployeeTree.Id 
    where  
        Employees.APV_MGR_EMP_ID is not null 
        and Employees.EMP_SRC_ID_NR is not null             
)
SELECT 
    Id AS [EmployeeId], 
    Uuid AS [EmployeeUuid], 
    ApprovalManagerId AS [ManagerId] 
FROM EmployeeTree