"3 strikes" for export failure (PL6)

When exporting photos, once 3 errors have occurred (due to missing watermark files in my case), the export simply hangs indefinitely and has to be cancelled.

This is easy to reproduce.

  1. Open a folder of, say, 10 images.
  2. Set a watermark image on 3 of the images.
  3. Move/rename/delete the reference watermark image.
  4. Export all 10 images.

I also note there are serious layout issues when errors occur and the export dropdown only has the one export batch present.