Resizing volume with DiskPart unsuccessful, while there's enough free space

It doesn't really matter whether its an OS disk or a data disk. In both cases, the middle of the disk is occupied by $MFTMirr which copies vital bits of the MFT Table. This file is unmovable, even though Microsoft made it available for moving since Windows XP.

So far I have found only one tool that can reliably move these files: PerfectDisk. It has a free, fully-functional, thirty-days version. It can only move these Metadata and MFT files when in offline mode: Select Boot Time on its main tab and either reboot or, if possible, defrag in offline mode. After this, the command SHRINK worked as expected.