I'd say two from the same user implies that the user is doing something different from other users.
Not hardware but a bug in chdk ( install process ) or a misunderstanding of something by the user.
Right, I'd like to know where I might have gone wrong then. This is my first attempt at asking a digital camera to boot anything other than the manufacturers OS and I think I've followed the directions pretty closely. The only deviation so far is the fact that sticks has a now-acknowledged bug and won't write correctly to SD cards on Ubuntu 16.04, so I ended up using licks. When I examine the SD card contents, from what I can tell, they do appear to be correct. Maybe it's just bad luck. I'm now forced to decide on trying to obtain yet another elph 160, or if I bite the bullet and buy a couple dlsr's. The bookscanner software maker pi-scan recommends Nikon 1 J5 for the DSLR (as of this writing) interfaced via libgphoto rather than chdk. Two new Nikon 1 J5's will cost me around $1000, which is a definite ouch. Currently, I'm out $100 in used cameras.
Well, with $1000 at stake I have another suggestion.
The ixus160 / elph160 CHDK build includes a ps.fi2 file. Which means that it supports
Firmware Update Method booting. You can simply low level reformat an SD card in your working camera and then use your PC to unzip the CHDK installation zip file (expanding directories) to the root folder on the SD card. No LICKS or STICK or any other special card formatting required. Start the camera by pressing the Playback switch (not the On/Off button) and then navigate the left hand tab Canon menu down to the bottom and select the "Firmware Update" option.
I guess it's possible that you will also brick your 3rd camera that way but it seems unlikely.
With my other option being $1000 in clunky DSLR's, I'd go for it. YMMV.