May be unable to a different location spatially, and instead just end up in the same location in a different timeline.
Protection conjecture, a cause that prevents the change of the past, could interfere with the Time Travel in some cases. If not and the past is change, results in the present time, before the travel, can have unwanted results.
Abuse of time travel may result in body aging back and forth repeatedly, until one achieves immortality, whether wanted or not. The body may have aged to either old or young, but one can no longer die or change in age any longer. Prime examples of people who have suffered such results include Professor Paradox and Porky Minch.
Cannot interfere in certain matters concerning the flow of time and space.
It's not known if the future is protected by the same cause the past is (see Precognition for more info how changes to the future could be prevented).
May distort the space-time continuum in exchange for traveling.
May only be able to transport living tissue through time.
Time travel to the past may create an alternate timeline, in order to prevent changes to affect the original time. This means that the past would branch off into a new dimension of time, while the present timeline would continue as though nothing affected the past. This prevents intended changes.