Net install of 9.6.0 breaks NTFS data access

[docduke]

Summary: A network installation of Debian 9.6.0 on an HP Elitebook 8570w appeared to go smoothly until I attempted to access the common data partition from another OS. The data partition is NTFS. The installer converted it to "fuseblk." That apparently altered the file structure sufficiently that neither Windows 7 nor Cinnamon Mint treats it the same as it did before. I request advice on (1) how to convert this partition back from fuseblk to NTFS, and (2) how to make sure Debian doesn't do this on another install.
Environment: On this computer, /dev/sda1 is the OS (root), sda2 is the swap partition, and sda3 is a common data partition, used by all operating systems. The boot manager rewrites the partition table at each boot, to point to the appropriate sda1, and the same sda2 and sda3 partitions, appropriate to the system being booted. The data partition now has about 430 GiB of data. It is fully backed up, but on an external device for which the backup took about 4 hours. I do not wish to do more than one restore of that data.
Issue: With Debian 9.5 on another computer with the same environment, "fdisk -l" returns:

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Device     Boot      Start        End    Sectors  Size Id Type
/dev/sda1  *    3529994580 3591427139   61432560 29.3G 83 Linux
/dev/sda2        614359185  681943184   67584000 32.2G 82 Linux swap / Solaris
/dev/sda3        681955716 3529994579 2848038864  1.3T  7 HPFS/NTFS/exFAT  

Note the last line. On the fresh Debian 9.6 install, the corresponding result is:

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Device     Boot     Start        End    Sectors   Size Id Type
/dev/sda1  *    389343232  450783231   61440000  29.3G 83 Linux
/dev/sda2       512223232  579326736   67103505    32G 82 Linux swap / Solaris
/dev/sda3       579332096 1945133055 1365800960 651.3G 83 Linux 

Again, note the last line. The sda3 partition is now identified as Linux. The Id has been changed. For more detail:

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zzz duke # df -Th
Filesystem     Type      Size    Used Avail Use% Mounted on
/dev/sda1      ext4       29G    5.5G   22G  20% /
/dev/sda3      fuseblk   652G    425G  228G  66% /mnt/ta8p

where the tempfs lines have been removed. My primary objective is to convert the partition back to NTFS and remove whatever changes make it look different. And it does look different. Booting Windows 7, the partition has disappeared, and Control Panel -> Administrative Services -> Computer Management -> Disk Management indicates that the partition is visible to it, looks "Simple" and "Basic" and "Healthy (Primary Partition)" but it doesn't know the File System type, and it thinks there is no data in the partition (Capacity = Free Space) which is definitely incorrect. The option to mount the partition is not available (grayed out). The only available option is to delete the volume. Booting Cinnamon Mint 18.3 for the first time, the "Files" app had an icon for "ta8p" in the left pane. Clicking on it got a message that the Mint could not mount it. On the second boot, the icon had been removed. I tried mounting it manually and got: Mount is denied because the NTFS volume is already exclusively opened. The volume may be already mounted, or another software may use it which could be identified for example by the help of the 'fuser' command. Note that "df" recognized the file system as fuseblk, but the "mount" command recognized it as NTFS. The mount was probably automatic, since the relevant lines of /etc/fstab are:

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# /mnt/ta8p was on /dev/sda3 during installation
UUID=01D1E9D2432ECE80 /mnt/ta8p       ntfs    defaults,umask=007,gid=46 0     0 

but the fdisk -l command reports:

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Device     Boot     Start        End    Sectors   Size Id Type
/dev/sda1  *    266463232  327902685   61439454  29.3G 83 Linux
/dev/sda2       512223232  579326736   67103505    32G 82 Linux swap / Solaris
/dev/sda3       579332096 1945133055 1365800960 651.3G 83 Linux 

and the relevant line of df -Th is:

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/dev/sda3      fuseblk   652G  425G  228G  66% /mnt/ta8p

Interpretation: Debian 9.6 altered this partition in a way that Debian 9.5 did not. It appears that no data loss occurred, but the partition has been rendered unreadable by Windows 7, and the Cinnamon Mint "Files app" is sufficiently uncomfortable with it that it will not leave a partition icon in the left pane.
Requested responses:
1. My primary objective is to reverse this conversion from NTFS to Linux fuseblk.
2. My secondary objective is to identify the trigger that caused this conversion, since the installer gave no indication that it was going to alter the partition. I want to be certain that this will not happen on future installations of Debian. If it is necessary to restore the data partition, I want to be certain Debian will not do this again when I mount it. I can think of several possible triggers:
(a) It came with the Debian 6.9.0 installer.
(b) It came with a network install. (All my previous Debian installs, and there are many, were from DVD-1 with network access turned off.)
(c) I did a Manual partition layout. I pressed "Edit" on /dev/sda3 because I wanted to assign it a mount point, and thought the installer might put that information into /etc/fstab as Cinnamon Mint did. After learning that option was not available, I exited with "No more changes."

Any help you can give me toward either of these objectives would be greatly appreciated. Thanks!

[dilberts_left_nut]

There is no "conversion".
The ntfs-3g kernel module uses FUSE to mount ntfs filesystems, hence the fuseblk device label in the df output.
It looks like your bootloader is misconfigured, or just messing with your head - note the different partition start/finish sectors in the fdisk output. I'm guessing they are completely different partitions.

[p.H]

The installer converted it to "fuseblk."

No it didn't. See dilberts_left_nut's reply.

The boot manager rewrites the partition table at each boot, to point to the appropriate sda1, and the same sda2 and sda3 partitions, appropriate to the system being booted.

This sounds like such a wrong way of doing things. What is this boot manager ?

The sda3 partition is now identified as Linux.

The partition type identifier is part of the partition table entry, not the partition contents. Didn't you wrote something about the boot manager mangling the partition table ?
By the way, the type ID is mostly irrelevant for Linux operation. GNU/Linux relies on other ways to discover a partition contents type. However it may be relevant for Windows operation, so feel free to change it back to NTFS with fdisk or any other partition manager.