For your experiment, are looking at measurements generated for each image (per-image, e.g, in a file called DefaultOUT_Image.xls) or generated for each object in an image (per-object, e.g, in a file called DefaultOUT_Nuclei.xls, or whatever your objects are called)?
If the measurements you are examining are per-image, then this would be odd behavior, since it should show at least an image number (if not more) for each image set.
If they are per-object, then this behavior can occur if no objects are being found in the "missing" images. You may want to generate a per-image spreadsheet (if you haven't already), and look at the object count under a column called "Count_" (where is the object in question). If those counts are zero for the image sets 1 through 9 and non-zero for the 10, you may want to check that your objects are being identified correctly.
Hope this helps!