1, Upgrade the boot version to 1.3.5.06 first, and upgrade the firmware to 1.3.5.58. Both of these files are in the 1.3.5.58 firmware zip file. Reboot.
2. Then upgrade the boot to 1.4.0.02 and the firmware to 1.4.0.88. Both of these files are in the 1.4.0.88 firmware zip file.
This way, the running firmware, at all times, is on a supported boot version. Your process may work without a hitch, but this way will make sure there is no mismatch between boot and firmware. Hopefully, this helps. Thanks Keith.