Repeating Room Glitch

The Repeating Room Glitch (a.k.a. The Room of Purgatory, Repeating Checkpoint Glitch, or simply known as the Repeating Glitch) is a glitch that occurs after you have passed all of the rooms (and Checkpoints) in the game. In most playthroughs, this is past 33,000 points, deep inside the third endless reset.

In the glitch, the stage will constantly repeat. While it is most common to have this glitch occur while the Random Rooms Glitch is active (and ball grind as well, a lot), you can access this after the 3rd endless mode by using the room generator if it generates favorable objects. (Or, you can just play the Random Rooms Glitch and stash up on hundreds of balls starting from Checkpoint 3, then play from there normally.)
 * This glitch can occur by ball grinding, with the Random Rooms Glitch for a very long period of time (ex. 1 hour).
 * This glitch is caused by the the game.xml Problem, which is that the game.xml file has only three "endless" rooms inside it.
 * Unlike other glitches, it's behavior is considered intentional.

Zen and Versus
Zen Mode has the repeating room glitch occur after a certain number of rooms, in which zone 1 rooms will repeatedly appear. Unlike the Repeating Room Glitch, it is not permanent.

Versus Mode appears not to have this glitch because the rooms become in random order after completing all the rooms.