While not all 9.7-inch iPad Pro users have reported problems, there have been a number of reports on the MacRumors forums and on social networks, suggesting the problem is widespread. Attempting to restore through iTunes doesn’t appear to resolve the issue.
I have the 256Gb cellular iPad Pro 9.7 and I’ve had this issue; OTA update fails at the “updating firmware” stage and no amount of iTunes recovery attempts work, whether to 9.3.2 or to 9.3.1 downloaded from ipsw.me. Calls to Apple Support have led me to a Genius Bar appointment where I think they’ll likely swap out the iPad for a new one, which matches with the experiences read about online. Poor QA from Apple on a brand new device.
UPDATE: After I managed to squeeze into a Genius Bar appointment at Covent Garden, I relayed my conversation with Apple Support, they ran their own attempt to install 9.3.2 (with the same Error 56 message) and then simply swapped it out for a new one. Their feedback was there was a firmware issue on a batch, which meant when 9.3.2 was installed it tripped something in the firmware which then produced the hardware error message. Despite this, am going to hold off on trying the update again until there’s a new release. Macworld have also picked up on this.
Interestingly, 3 staff said this was only the 2nd iPad Pro 9.7″ they’d seen, with the first having just a cracked a screen.