When shooting TNT at a sufficiently high velocity, the entity appears to jump midway through its its trajectory. This affects most TNT cannons and can be best demonstrated with a high rate of fire cannon such as repeating command blocks using the summon command or rapid fire dispenser cannons.

If the primed TNT explodes before this "jump", it does so at a location inconsistent with how its trajectory is visually rendered, instead following the trajectory had it "jumped". A tad difficult to see, but this is shown in 2016-07-13_00.14.08_2.png

EDIT:
I have made a video to better show this bug in action.
https://youtu.be/x8xrLEDV-wY