In short, all bugs introduced with the latest Canon camera releases are present in the RAW files.
First, just like the 1D X Mark II, ISOs above 51200 recorded in the EXIF incorrectly as 65535 by the camera. The screen shot on the left shows an ISO 102400 file from the 5D Mark IV. This is something that affects users and can’t be corrected in Kuuvik Capture. So if you are running into this: it’s a problem with the camera firmware, not with the app.
Second, internal lossless jpeg headers are corrupt exactly the same way the 5DS/R screws these up. Kuuvik Capture works around this bug, so it’s not something you’ll notice, just annoying to witness.
Third, the whole question of ISO 32000. Since 1/3 stop ISO values are digital trickery, the camera’s top ISO is still 25600. But it seems that marketing folks were not satisfied with that. So the fake top ISO was born. I saw this in the 7D Mark II for the first time (ISO 16000), and it seems that they are so fond of this that the 5D Mark IV also got it. The app handles it correctly, it’s just something you need to be aware of as an informed user.
Of course the upcoming version 2.5 will have full 5D Mark IV support, just wanted to share the progress with you. We plan to release version 2.5 later this fall. It will be a free update for all Kuuvik Capture 2 users.