@Mihail_Isakov I do not have any experience with or access to the tool you are using, or to its source code, and I didn’t investigate the content of those files. All I know is that if I use established open source tools that I trust, I do not see inconsistency in how images show up in Slicer. I would be very surprised if dcm2niix didn’t sort frames, and that’s what I used to load the multiframe image into Slicer.
I won’t have time to debug this any time soon. But I also won’t take a screenshot from an unknown tool as a proof that data encoding by David Clunie is incorrect