Weird problem with tempo

[pdk_]

Here is the problem I am facing. I export a track (lets say 120bpm). Then I want to insert this track into a new project.In the new project I make tempo changes for each track. I do that cause i want to cut the tracks and make them loops. The weird thing is that sometimes the track is shorter or longer than the end bar when i zoom too close. I figure this out cause some loops sounded choppy or had silence. Its the same tempo, no other program involved. I just insert the tracks from the filemanager of waveform. Does anyone had a similar thing happened? Is this a bug?