In Nebulb, each processing performed is stored in a self-contained project file (files with extension *.nbp), in which Nebulb saves all the information generated during stacking and, also, all the processing settings applied by the user.
That is, the project files contain all the necessary information to be able to apply all the desired adjustments on the image resulting from the stacking (without the need to have the original image files).
That said, the original images imported into Nebulb cannot be included in the project file, as they take up too much space. A reference (link) to the location of the original images is stored in the Nebulb project file.
Therefore, if you move the images to another directory (or rename the folder containing them) Nebulb displays the following message indicating that it cannot find the imported images: "Some images of the project could not be loaded because their files could not be found"

However, it is very easy to solve this problem, since Nebulb (since version 1.6.4) allows you to update the path of imported images.
To achieve this you simply need to do the following::
1. Click on the main menu option: “Edit --> Update the path of imported images”
2. Select the folder in which the images are now located.
When doing the above, Nebulb checks if the imported images are in the new location, updates its internal references (links) and finally displays the following confirmation message: “The path of all images has been correctly updated"
Now all you have to do is save the project and the next time you open it, you will no longer get the warning that Nebulb cannot find the imported images.