Export function exports different to timeline, parts missing

When I try to export my vid (out:mp4, 30fps - source mov/30fps) the output file is not e.g. 15mins like showed in the timline, its just 13m44s.
So shotcut just alters the cutting points of a clip and makes it shorter than in the timeline indicated. This can occour at different places in the vid and is not predicable (for me).
This is really odd, because you dont recoginze this immediately if you are not looking very close to the time of the exported vid.

I do not know how to reproduce this. There have been some issues when people change the Frame rate in Export, but that should be fixed in the latest version 18.09.16. You did not specify your version (see Help > About Shotcut) or any of your export settings.

i maked a project and save that but when i load that it is very Compressed and when i play project The time for that project end very soon . i dont know why my project become compressed.

Your screenshot shows that the timeline has 24 clips in it, each one being 1 frame in length.

I would suggest that at the very least you post the MLT file and the logfile otherwise it is unlikely anyone will be able to figure out what is happening.