When you put too many TNT minecarts on one rail, break it and push it, they go in the direction you pushed them until they either crash into a wall or fall and then explode. And they explode weirdly (at least for me). They go boom boom in a vertical line and TNT minecarts also spin vertically and SO FAST due to a weird game mechanic I think.

Note: I don't know if it's a bug

Note: The video needed to be 10 megabytes so it's 3 seconds hope you understand it