Using image Labeler to create ground truth data

I am using the image Labeler to create ground truth data which will be further used to train the ACF Object detector. However, I am facing some issue with the image Labeler app. I am not able to use more than 23 images in the image Labeler app that is I am able to load more images into the app, however, when I press the Automate button after choosing the ACF people detector algorithm for the 24th image, it generates the error message in the command window. I am attaching a screenshot for your reference. Please check that and suggest a way to overcome it.

[M.Khan]

Which version of MATLAB are you using? Is the issue sporadic or does it happen everytime you select more than 23 images to run ACF people detector algorithm? Does ACF Vehicle detector work fine for more than 23 images? Thanks.