BFC - many thanks and I echo your 'hopes' for comments.
More likely, however, is that the plane was left in AIR MODE on the ground after the pressurization test carried out three hours before the last flight
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on a quick read through your post only, this would have been instantly noticeable to the pilots as they would not have been able to select the APU electrics onto both generator buses before start, as that function is 'ground mode only' on the Classic 737. This would have caused several problems with systems etc during the pre-flight preparation and taxy.
I'm still not aware from any reports as to when the horn began sounding? Do you know?
To add that anyone wishing to contribute 'off-line' is welcome to PM me and I will de-identify and post if I consider it suitable material.