This is normally caused by a storage issue on the device. Try deleting photos from the gallery and any unused applications
If you are using an Android tablet you may need to delete files from within the Kaptur app. Navigate to the PIMS Sync tab which can be found in the dropdown menu and then you will need to empty the dustbin at the bottom of the page labelled PIMS Files. You could also change the job parameters that you will find in the settings tab. The previous and future jobs should be set to 1 week.