The example bootloader hex files within SDK 15.3 will load on the development board and seems to provide connection through nRF toolbox on a iphone 7 but will not load on custom hardware. The custom boards are fairly mature and have had good success with other applications. The development has been through the armgcc and therefore utilizes the command line tools. The specific command to program the both the development board and my custom hardware was: nrfjprog --reset --program sd_s132_bootloader_buttonless_with_setting_page_dfu_secure_ble_debug_without_bonds.hex --family NRF52 --sectoranduicrerase which was suggested from the online SDK 15.3 examples documentation.
When trying to program custom boards through the development board the command line tools suggest that the hex file is not valid as the data is either in or out of the valid area. Any help would be appreciated.