Hello @DilumCoppens1
It looks like you are using georeferenced images.
Can you try to turn off the camera priors (select all images in 1Ds view and set the Prior pose/Absolute pose to Unknown in the Selected inputs panel. After that process your project again and then try to export the masks.
Yeah, I think that was the problem. Solved it 2 days ago.
If anyone ever had the same problem: the solution I figured out is to disable the GPS coordinates in the settings when aligning the images. I think that, because the GPS coordinates were pointed in the model (smartphone GPS), it didn’t properly generated the masks. Disabling this function solved it.