What is your operating system?
What is your Shotcut version (see Help > About Shotcut)?
Can you repeat the problem? If so, what are the steps?
my project is built from an hour-and-a-half-long audio and three 30 ish minutes videos.
the last one will upload the first seven min and then just blackout. when i open the file on my video player on the PC there will be no problem. but on shotcut the video stops and the track will turn into a straight line.