Strange that it should ask to update mid gig then as the fw must have been there from when you switched it all on.
On a similar note. I had a slightly, lets say "non-optimum" time last night, I was running PA for a charity event with four acts from a duo to a four piece electric band. I was using my X32 (DL1608 in the car as backup) and didn't take my Airport Extreme router which is set up for my X32 but used the Airport Express that usually lives with the DL. I had made the settings identical to make them interchangeable but, while the iPad connected to the Express the Airport app told me the Express needed to update and, as there was no internet (or mobile signal) at the venue, this was not possible. I managed fine running from the desk but without faders it might have been another story. The sequel is that the X32 connected back to the Extreme the moment I got it home and I then plugged the Express to the DL and fired than up with the same result (and no update request)!