Since you have upgraded one device successfully, we can take a snapshot from that device and get this device upgraded.
Step 1. Plugin USB to upgraded device and issue " root> request system snapshot media usb partition". Thiss may take few minutess (5-15)
Step 2. Power down the device facing upgrade issue
Step 3. Plugin USB with snapshot to device facing upgrade issue
Step 4 . Power on device facing upgrade issue, device will automatically try to boot from USB
Step 5. Once device booted up execute below command to cpy snapshot to internal flash
" srx> request system snapshot media internal partition"
Step 6. Once step 5 is completed you may plug out the USB and try reboot to verify the device is booting up with new version.