My CTE runs in an infinite loop for a specific customer and I am not able to find out why.

Here is the query:

;WITH ClassTree
           AS (SELECT ID, NAME, Parent_ID
               FROM   TableName
               WHERE  ID = 1
               UNION ALL
               SELECT T.ID, T.NAME, T.Parent_ID
               FROM   TableName T WITH (NOLOCK)
                      JOIN ClassTree
                        ON Parent_ID = ClassTree.ID
)
SELECT * FROM ClassTree



Question: Where do the bodies of the dead Tributes go?
Answer: Hovercrafts are instantly dispatched to recover the body, perhaps to prevent cannibalism, which was an issue in previous Games:


  There was a guy like that a few years ago from District 6 called Titus. He went completely savage and the Gamemakers had to have him stunned with electric guns to collect the bodies of the players he'd killed before he ate them. There are no rules in the arena, but cannibalism doesn't play well with the Capitol audience, so they tried to head it off. There was some speculation that the avalanche that finally took Titus out was specifically engineered to ensure the victor was not a lunatic.


And on the hovercraft to retrieve bodies quickly:


  Suddenly, the birds fall silent. Then one gives a high-pitched warning call. A single note. Just like the one Gale and I heard when the redheaded Avox girl was caught. High above the dying campfire a hovercraft materializes. A set of huge metal teeth drops down. Slowly, gently, the dead tribute girl is lifted into the hovercraft. Then it vanishes. The birds resume their song.


This may have been the same hovercraft: