High acceleration of the sound of the mp4!

I am convinced that this software is regularly modified without the modifications being tested beforehand. I run yesterday the 20.02.17 version four times and I obtained (only once time) a high acceleration of an old mp4 and modification of this sound
the mp4 and the application are on the hard disk. If I run the mp4 outside of shotcut, no problem with the sound
Yesterday, only one time, I run one of my (very correct) .mp4 and the sound was accelerated by about 50% and modifications. I went out of shotcut, rerun shotcut and … no problem with my mp4 : I could add a subtitle

Today : i run outside of shotcut a new (on hard drive) mp4 : no problem. I run ten times successively this mp4 under shotcut and acceleration of mp4 each time. I restard my win10 and the problem is still here !!
Now I test an old version : 190914
190914 and the .mp4 are exactly at the same directory of my usb key. The bug is allways here and no problem with the soundtrack if I ear outside of shotcut.
So, one more time, I’m blocked !

however, these 2 defects do not appear in the exported file
!!!

So I’m not blocked :smiley: