I will try to make a fresh copy of CHDK and the script in the evening.
It will not hurt to try this but I don't think there is anything wrong with your CHDK installation or how the script is installed.
Yes you are definitly right, but first things first.
In the morning in bright sunlight I tried again with the given setup,
but no other reaction.
So I setup a new SDcard with CHDK and the script
and I reset the canon setup (I had issues with that in the past),
but also the the same reaction.
I told you, when I press the review button, then I switch over to another picture.
That's shure.
The very first picture taken is very dark (underexposed; IMG_8828.JPG).
In the KAP.LOG you will find only the underexposed pictures.(IMG_8828.JPG,IMG_8830.JPG,IMG_8832.JPG)
Pay attention to the numbering.
But there were well exposed pictures IMG_8829.JPG,IMG_8831.JPG,IMG_8833.JPG, taken when I press the review key and they are stored.
Immediatly after that well exposed picture the next underexposed picture is taken automaticly and the picture stays on the screen.
Pressing review key works again ... and so on.
When I press the menu key quick enough, then the script is canceled in a korrekt way, as you see in the log.