I know that this should be filed through GitHub but it is very difficult to register on GitHub with my configuration so I’m hoping this will be seen here and posted as an issue by somebody who cares.
The issue is with qvm-copy/qvm-move when selected via the GUI. Basically the call to du can end up being less than the actual size of the files to copy/move and then zenity will auto-close prematurely which will result in the entire copy/move exiting prematurely. None of this is indicated to the user. This is bad because unless the user manually verifies that the copy succeeded they can unknowingly miss files. This happened to me in practice when trying to copy a git repository.
I think the flags that needed to be added to the du call are -l and -L although I am not certain this will cover every case. Perhaps du is not even the appropriate way to handle this sort of calculation.
You should be able to reproduce this by cloning a git repository and then copying it to another appvm.
This is the relevant file: