Cannot boot to boot camp Windows after shrinking the Mac os partition

Also, I just went ahead and did the bootrec thing. At first the bootrec /rebuildbcd said something like "could not write to disk" (fixmbr and fixboot was fine though).

Then, I rebuilt the Windows Installation boot disk (I downloaded the ISO from Microsoft website instead of using my original Win 10 enterprise ISO) in Rufus, using the non-UEFI option this time ("Legacy BIOS CSM"?).

This time, the other two worked, but /fixboot reported "Access denied". I tried rebooting anyway, AAAAAND....

I saw my Win 10 desktop again! It worked! You are the man LT!

What I did was telling winclone to back up the windows partition to my 2tb external USB disk

A few more questions:

1. If I am to back up the bootcamp partition, can I use WinClone?
2. To GParted, expanding the bootcamp partition to take up the free space of disk0s4 is like expanding an ordinary GPT partition, right? From the perspective of Windows, nothing has changed, since the MBR info before and after the expansion stays the same (by using GPT fdisk I saw that it contains a protective MBR instead of a Hybrid so I think all of the MBR info is toast) .... What I'm trying to say is, I might consider to leave the free space alone and just make Windows bootable again, if the GParted expansion thing is risky or something... so if I leave the space alone, I just need to use the USB Installer, right?
3. Is a (pure) GPT-based Windows 10 more performant than a Hybrid-MBR? I'm not sure if it is Hybrid or not before I screwed the disk up. I think now it is already a GPT partition. Would the USB installer hybridize the partition again?

If the de-hybridize thing makes things complicated to you, then forget it (I think it might need reinstalling Windows anyway... even if it doesn't, if it makes the config more prone to errors/config mistakes or incompatible with Apple stuffs, then I will just give it up) ... Sorry for having so many questions!

Hi LT, sorry for being MIA for so long. Here's the update:

1. bootcamp backed up
2. used diskutil and GParted to expand the bootcamp partition (I allocated a further like 50GB of space)
3. used the win 10 installer to do "startup repair"

During the time it was smooth and uneventful.

But unlike what I expected, after all of those, I wasn't able to boot windows up ("Missing Operating System")

My installer USB is created in Rufus with the UEFI option selected, does it matter?

Or, in gdisk I spotted the "SIP not deactivated" thing, I think I have missed that out, but would like to know I should redo it at this stage.

I didn't use Winclone to alter disk0's partition, but I used "disk utility (GUI)" (shrinking Mac Partition) and GParted (expand bootcamp) to do so.

So in other words I only used one tool on the bootcamp one.

Do I really need to use BCA to remove Windows and restore the backup? I do have a backup, but am wondering what is out of order? Seems to me that disk0 is already in GPT format already, before I used GParted (unless I got the meaning of the output below wrong):

(Quoted from the text of the question:)

xxxx$ diskutil list

/dev/disk0 (internal, physical):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                        *500.3 GB   disk0

   1:                        EFI EFI                     209.7 MB   disk0s1

   2:                  Apple_HFS Macintosh HD            120.1 GB   disk0s2

   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

   4:                  Apple_HFS Untitled                29.2 GB    disk0s4

   5:       Microsoft Basic Data BOOTCAMP                350.0 GB   disk0s5

Also, I can see the bootcamp drive in Finder, I picked a few text files for a look, seems fine to me.

I'm a bit panicking tbh.

I have been following method 1.

Since I think I've done (1) and (2), is it "Recreate MBR" that I missed, causing (4) to fail?

Also, the partition sizes of gdisk and diskutil list seem to be out-of-sync (e.g. 619.9 vs 650 for "Recovery HD"), I'm worrying that I made something wrong previously.

Again, thanks for your patience!

After 12 & 13, it said failed to write to disk

I've rebooted to Mac's recovery partition and did csrutil disable, and redo it from step one to the last. I reboot straight into Windows and it said an error occurred, like winload.exe and code 0x0000225, and "a required file is missing or contains errors".

I searched for the error and seems that it means the .efi file is missing.

Should I use the windows installation USB to perform the startup repair?

Dang! I thought it should be disk0 instead of rdisk0 and the screenshots are actually from the results of gdisk /dev/disk0.

Does it made any difference? Seems that my mistake is benign and doesn't change much to the disk

It's late now and I think I would come back to the problem when I'm able to do so

The ms document said I should try automatic repair first before using bootrec.exe, so should I do so?

Also I did that once already (auto repair), without any effect, would bootrec (/fixXXX and etc) do something that auto repair don't?

For the three kinds of op of bootrec, the fixXXX ones only write to the protective mbr area, so if they put the wrong stuffs, we just rebuild the mbr, right?

Also, what's the difference between fix boot and fixmbr? From what m$ said they either deal with the boot sector or (mbr minus its partition table). They are pretty much the same to me.

Anyway, if these things are more or less figured out I would proceed to try automatic repair, and then the three bootrec commands.