What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit?
21.10.31 How do I tell how many bits
Can you repeat the problem? If so, what are the steps?
I import some video from a wedding in the first video track. Then add an audio track below it. After listening to the audio track I highlight it, split the track and ‘remove’ the first piece - the video above it gets removed as well. I tried removing the entire audio track and all the video got removed as well. I eventually had to slide my video a few minutes to the right to line up with where the audio starts, process the video, import it again then cut the beginning shorter as a workaround.