Music cut

[Polop]

Hi,
I use MM 5.0.2 and, sometime, my music is cutting when I lesson it.
In the list of part of music, under time, there is an orange line. Sometime this line is long or short (see screen copy).
When the line of a song is on the middle (for example) the song begin in the middle.
How can I have all my song begin in the beginning ?
Thanks for your help.

https://drive.google.com/file/d/1QNzuAP ... share_link

Pierre