In 13.0.48, this works as expected if the results are shown in the destination.
If they are shown in the source, the focus is on the source, and the only way to bring it back to the panel to use the accelerator key is to close and re-open the panel. After selecting files through the dialog, the panel needs to be closed again to bring the focus back to the file display and be able to e.g. delete files.
When you saw that last problem, was the panel visible but couldn't be clicked on until closed & re-opened?
If so, I have an idea what might cause that, and we have a fix in the next beta if it's the same problem I'm thinking of. Either way, let us know if you see it again.