I am using MATLAB version 2019b. The issue is that the Image labeler session when saved does not save/store the label data correctly. When the saved session is re-opened, the label data loads as annotations/boxes on the images but when exported label data is empty. However, data for any changes/edits made to the images within the current session gets exported fine.
Here is another interesting find: All data is exported correctly from a re-opened session when there are no attributes present. The above issue happens only when attributes are associated to the labels.
Is this a bug with the 2019 beta version and being looked into?