I have seen 2 solutions here on this topic. But both were solved by rewriting the MLT file in Notepad. Which is a really long process. YOU DON"T HAVE TO DO THAT.
If you noticed that after rendering, shotcut rendered the proxy file instead of the original. Then your resource file is replaced by the proxy file. Here’s how I fixed it,
Step-1: Open Your MLT file and turn of the “use proxy” settings. Now the files on your project
will transform from proxy to resource. But because your resource file is replaced, the
files are still at 360p. Then close your MLT file.
Step-2: Write down your resource file name and their proxy name side by side. Then move
your proxy files to another folder. You can delete them. But I keep them just in case
this doesn’t work.
Step-3: Open your MLT file again. This time it will show that some files are missing. But the
file names are proxy name. Now double click on them and replace those proxy files
with the original. It should solve the problem.
English isn’t my first laguage. So I hope you understood this.