torrent mixes video files

[helpmepls]

when i am torrenting multiple video files, after they have finished, they all work. but sometimes i have a video file that that is exactly like another when it's supposed to be something different.

for example:

i download 2 video files, 1st one would be called "abc.avi" and the 2nd would be called "123.avi" and they're both saved in the same drive but in different directories. they're both different filename, different file sizes but when i play them, they both appear to be only of one of the video files, so "123.avi" would be exactly the same as "abc.avi" even though it has a different file name and different file size.

anyone know what the problem is? and how to fix it?