Firmware updates are always tricky propositions, especially in units as technologically sophisticated as the 436 and 536 scanners. As I mentioned in another post, one of the issues with the current update should have been caught before release---- it's hard for me to understand how the USB cabling issue (auto switch to serial after 10 seconds) could be released with everyone seeming to have the problem with its not working. This is probably linked somehow with the new version of Sentinel and my guess if that something got skewed in the release. This is a fault that is most likely attributed to sloppiness on the part of Uniden.
The issue with the squelch/backlighting is a something a little different. You may have five or six engineers running through the effects of adding OFF to the replay menu with regard to some of the "typical" functions of the unit. But with units like the 436 and 536, there are so many possible permutations of functions that it is more likely, as has happened in this case, that the end users, who number is the thousands, are going to hit on a feature or function or combination thereof, that has been inadvertently and negatively affected by the change.
This is going to be the case with every firmware update, and becomes exponentially more troublesome when you see releases that incorporate updates to more than just one or two functions. As an example, I recall participating in some "minor" changes to an emergency services dispatch system, and the end result was that each single line of code that was either added, deleted, or changed in the firmware ended up requiring nearly 50 pages of notes to document the change.
The bottom line is that some things, like the USB cable issue, should have been caught by Uniden, but other changes are more likely going to be caught by us guys (and gals) who use these radios in a myriad of different configurations, every single day.