jondc9, the issue for me is not really about humans failing to notice their Xponder was off or on SBY for so long, , but the sofware trap that caused the system to shut down that way, and the HMI design that prevented the crew from noticing it.
Because it happened before ( in Switserland and France recently, both involving E145 with Primus ), and so, most probably, it will happen again .
The idiocy of this is that by switching itself off, it also disable ( ACAS) as well.
So the end result of this is depriving you in one go of your 2 main anticollison systems : ATC and ACAS.
This is half of the cause of this collision. The other half is on the ground and there apparently, also caused by 2 software traps that led the controllers to beleive the aircrfat was not at the altitude he actually was .
I think we should far more focus on HMI and computers/man decisions processes integration than about blaming their operators .
But this is far less popular.