Thanks, Pask, I know this is frustrating, I had a similar problem at the very beginning when I was connecting my Nikon D3300 to Indi and it would always crash. I do not remember exactly anymore how I solved it, now I am trying to retrace my steps. Also, this is kind of a fun detective game and it helps me also understand the programs and the integration of the different parts into Indi better. So I have to beg you and Jasem to have patience with me, not the other way round.
I looked at your log file and from what I am seeing all goes well with the camera connecting, taking a 10s exposure and then it falls apart due to an 'Unknown event'. That doesn't tell me (at least) anything, except that something went wrong. I can deduce that from the ensuing crash. That's why I proposed to start at the very beginning of the problem, i.e. gphoto2. It could be a gphoto driver problem, as Jasem suspects, or it could be Pi3-related hardware limitations with just too big a data file coming in and the Pi can't handle it. That's my pet theory here. To distinguish between the two I suggested a very simple test: Stop Indi, quit Kstars, open a terminal and simply paste the following commands:
$ cd ~/Pictures
(so that the tmp file I am interested in gets temporarily saved in the same folder as the final image file downloaded from your Canon instead of the /home folder and so you don't clutter your home folder with files you want to manually delete again later)
$ gphoto2 --capture-image-and-download --filename ~/Pictures/Test.CR2 && eom ~/Pictures/Test.CR2
(this will command your Canon to take an image at the settings you specified on your Canon, i.e. with exposure time and the format settings RAW, mRAW or sRAW that you have specified there, then download it to the Pictures folder, calling it Test.CR2, and once that is done open it using the Eye of Mate image viewer. If this all works, then this would likely not be a gphoto problem, but I suspect it will fail)
This is what you should see if gphoto completes the task successfully (not that because I do not have a Canon, but a Nikon, the file is called Test.NEF):
If you are paying close attention to the Terminal after pressing 'Enter', you will briefly see a download bar/notification appear that gphoto is now downloading and saving the file. As you can see from the screenshot, the file will now appear as Test.NEF in my Pictures folder and EoM shows a red image (since my telescope has filter mounted and it is just pointing at my wall inside the house).
If you now repeat the last command again, i.e. take the picture and have it downloaded (you have to close the image window first, because that process is still running in the terminal), gphoto will note that there is already a picture present with the same name and ask you whether you want to overwrite it or give it a new name. That in itself is not important, what is important is that gphoto saves an intermediate tmpfile until you have made up your mind about what to do with it:
It is this tmpfile I am interested in, because the size of it will tell us whether gphoto starts to download the file from your Canon and then gets overwhelmed by the size and aborts, leaving a truncated tmpfile behind, or whether it doesn't start at all. If it doesn't start at all, this would point to a driver problem inasmuch as there is an issue with initiating the download of a full size RAW file, and then that would indeed be a problem for the gphoto development team. If it, however, downloads the file in part and then aborts along the way, that might suggest to me that the Pi3 hardware can't handle the data influx from the large file and crashes at that point.
Do this with the camera settings at sRAW, mRAW and RAW. According to what you wrote before, sRAW and mRAW files were no problem, so they should complete in this simple test as well, while full RAW images crash the program.
It would be interesting for me to see what happens. I would predict that you will end up with a tmpfile of approximately 35MB when you use full RAW and gphoto gets stuck.
Bonne chance!
Jo