Suddenly getting "There is no operating system installed in this virtual machine."

Technical Report ID: 480494889
Had a similar (the same?) thing happen half a year ago and ultimately needed to create a new VM. I'd rather not repeat the process if I can help it.
Earlier today, Parallels apparently got stuck trying to suspend the VM; it kept spinning in Control Center. It wouldn't react to quitting, or even force-quitting. Only by killing prl_disp_service did the UI become responsive again. But afterwards, the VM would no longer boot.
I see some "consistency check" messages in the log:

01-15 23:09:47.590 F /LocalDevices:1323:3895/ [hdd::sata:0] Connecting device "/Users/chucker/Parallels/Windows 11 (1).pvm/harddisk.hdd"
01-15 23:09:47.592 F /dimg:1323:3895/ Image was incorrectly closed!! Consistency check must be performed
01-15 23:09:47.592 F /dimg:1323:3895/ STRUCTURED_INFO:
01-15 23:09:47.592 F /dimg:1323:3895/ Element size: 4
01-15 23:09:47.592 F /dimg:1323:3895/ Element granularity 1
01-15 23:09:47.592 F /dimg:1323:3895/ Block size 2048 sect
01-15 23:09:47.592 F /dimg:1323:3895/ BAT offset 64 bytes
01-15 23:09:47.592 F /dimg:1323:3895/ Data offset 2097152 bytes
01-15 23:09:47.592 F /dimg:1323:3895/ Prefix size 0 bytes
01-15 23:09:47.592 F /dimg:1323:3895/ Postfix size 0 bytes
01-15 23:09:47.592 F /dimg:1323:3895/ Footer size 0 bytes
01-15 23:09:47.592 F /dimg:1323:3895/ CCompImage::IMAGE_PARAMETERS
01-15 23:09:47.592 F /dimg:1323:3895/ Signature: [WithoutFreeSpace]
01-15 23:09:47.592 F /dimg:1323:3895/ Disk type: 2
01-15 23:09:47.592 F /dimg:1323:3895/ CHS: 1048576-16-2048
01-15 23:09:47.592 F /dimg:1323:3895/ BAT size (# of blocks): 262144
01-15 23:09:47.592 F /dimg:1323:3895/ Size of disk in sectors: 536870912
01-15 23:09:47.592 F /dimg:1323:3895/ Disk is in use: 0x746F6E59
01-15 23:09:47.592 F /dimg:1323:3895/ First data block offset: 4096 sectors (2097152 bytes)
01-15 23:09:47.592 F /dimg:1323:3895/ Flags: 0x0
01-15 23:09:47.592 F /dimg:1323:3895/ Error 0x80021047 when opening the disk. Releasing image.
01-15 23:09:47.592 F /vdisk:1323:3895/ Storage[0]: consistency check needed for image '{5fbaabe3-6958-40ff-92a7-860e329aab41}' name '/Users/chucker/Parallels/Windows 11 (1).pvm/harddisk.hdd/harddisk.hdd.0.{5fbaabe3-6958-40ff-92a7-860e329aab41}.hds'
01-15 23:09:47.592 F /vdisk:1323:3895/ OpenDisk() returned error PRL_ERR_DISK_INCORRECTLY_CLOSED (0x80021047)
01-15 23:09:47.593 W /vdisk:1323:3895/ Consistency check is required for disk '/Users/chucker/Parallels/Windows 11 (1).pvm/harddisk.hdd'
01-15 23:09:54.297 W /HddUtils:1323:3895/ HddCheckConsistency: fragmentation ratio calculation done
01-15 23:09:54.299 W /vdisk:1323:3895/ Disk operation 'FixConsistency' requested.
01-15 23:09:54.300 W /dimg:1323:3895/ [Reclaim] Disk has data (BATend = 1048640, file size = 164900110336)
01-15 23:09:54.300 W /dimg:1323:3895/ [Reclaim] New first block offset = 4294967295 sectors
01-15 23:09:54.300 W /dimg:1323:3895/ [Reclaim] Processing image: /Users/chucker/Parallels/Windows 11 (1).pvm/harddisk.hdd/harddisk.hdd.0.{5fbaabe3-6958-40ff-92a7-860e329aab41}.hds
01-15 23:09:54.300 W /dimg:1323:3895/ [Reclaim] Creating map of all referenced blocks and duplicated blocks
01-15 23:09:54.331 W /dimg:1323:3895/ ConsistencyCheck: duplicated blocks = 0
01-15 23:09:54.331 W /dimg:1323:3895/ ConsistencyCheck: unreferenced blocks = 0
01-15 23:09:54.331 W /dimg:1323:3895/ ConsistencyCheck: unaligned blocks = 0
01-15 23:09:54.331 W /dimg:1323:3895/ ConsistencyCheck: out of disk blocks = 0
01-15 23:09:54.331 W /dimg:1323:3895/ ConsistencyCheck: blocks in BAT = 0
01-15 23:09:54.331 W /dimg:1323:3895/ ConsistencyCheck: blocks unused by guest = 0
01-15 23:09:54.331 W /dimg:1323:3895/ ConsistencyCheck: blocks truncated after fix = 0
01-15 23:09:54.331 W /dimg:1323:3895/ ConsistencyCheck: referenced blocks = 157259
01-15 23:09:54.331 W /dimg:1323:3895/ [Reclaim] LastUsedBlockEnd: 322070528
01-15 23:09:54.331 W /dimg:1323:3895/ [Reclaim] Image marked as non-empty
01-15 23:09:54.331 W /dimg:1323:3895/ [Reclaim] Nothing to truncate!
01-15 23:09:54.344 W /HddUtils:1323:3895/ HddCheckConsistency: operation completed, error PRL_ERR_SUCCESS
01-15 23:09:54.344 W /vdisk:1323:3895/ [harddisk SSD] Disk operation commited with result PRL_ERR_SUCCESS
01-15 23:09:54.344 W /vdisk:1323:3895/ [harddisk SSD] Disk operation finished with result PRL_ERR_SUCCESS
01-15 23:09:54.344 W /vdisk:1323:3895/ DiskCheckConsistency: done
01-15 23:09:54.346 F /AbstractFile:1323:3895/ open64() error: 2, flags = 0x2, disp = 0x1000000
01-15 23:09:54.346 W /vdisk:1323:3895/ disk is reopened after consistency check​

But that looks successful to me?
Despite that, I get

There is no operating system installed in this virtual machine.
To install an OS, connect a source with OS installation files, such as a CD, thumb drive, or disk image, and reset the virtual machine. For more information, see Parallels Desktop Help.​

Parallels then goes to a boot manager, where Windows Boot Manager is an option that seemingly does nothing, and UEFI Shell gives me a shell. (I'm unsure how to use it. "exit" works and takes me straight back to the Windows Boot Manager.)

Using Parallels Mounter, I can see that at least some of the data is there. It's unclear to me if the error means

a) the boot manager (EFI file?) is broken, and needs to be recreated
b) the boot manager has the wrong EFI file path
c) there isn't much of an OS left to recover

 

Wait.
I went back to the UEFI shell, left it running, went to Parallels's Actions menu, Reset, and... Windows booted.
Someone explain this one to me. :-|