Ultra+ 256GB error on first POST only

The update pull explination is in the FW thread

http://forums.sandisk.com/t5/SanDisk-Ultra-Plus-SSD/Ultra-SSD-Firmware-Version-X2306RL-released/td-p/294746

" Notice for users that Previously upgraded to Firmware Version X2316RL

Some systems have a compatibility issue with the USB or CD-ROM bootable system image and the FFU does not start or fails during the FW update process. There are no issues with the firmware and if you previously upgraded successfully you will not be affected by this issue. While we investigate this matter, we have decided to remove the new firmware from the SSD Toolkit"