This error means that 3Dsurvey was not able to delete the contents of the temporary folder, which is located where your images are, inside 3Dproject/temp folder.
Usually this is because that folder is open in explorer, or a file in that folder is open in another program.
You can just try clicking on bundle adjustment a few times. If that doesn't help, try saving project, restart your computer, open the project again, and try running bundle adjustment again.
If it still doesn't work, let me know, we can schedule an online meeting to sort it out.