Time Loop
A Time Loop is a distortion in the Fourth Dimension where time folds back on itself. A TARDIS can be programmed to time loop an area at least 100 meters long. This is very difficult to do and results in a TARDIS (and the operator) being trapped in the Time Loop. It is possible for a TARDIS to escape from the Loop, but this is even more difficult to achieve. Stopping the Time Rotor while in Vortex might allow a TARDIS to escape from some types of Time Loops (but not Chronic Hysteresis).
It is possible for a vessel trapped in a Time Loop to be forced free by another TARDIS in the Vortex.