External Hard Drive "The backup GPT table is corrupt"

So, I recently installed Ubuntu on my old laptop after using Windows 10.
I was using an external HardDrive (Seagate Backup Portable 4TB – formatted as NTFS) on windows, that I started using on Ubuntu.
When I opened GParted, I was given the message:

The backup GPT table is corrupt, but the primary appears OK, so that will be used.

I found some answers (1) that had some similarities to my issue and I tried them but didn’t work.

Here is the result of sudo sfdisk -l /dev/sdb

The backup GPT table is corrupt, but the primary appears OK, so that will be used.
Disk /dev/sdb: 3,65 TiB, 4000787029504 bytes, 7814037167 sectors
Disk model: BUP BK          
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: F33087C3-E03F-4A5A-A52A-2D5C30471082

Device      Start        End    Sectors  Size Type
/dev/sdb1      34     262177     262144  128M Microsoft reserved
/dev/sdb2  264192 7814035455 7813771264  3,7T Microsoft basic data

Partition 1 does not start on physical sector boundary.

and the result of gdisk p command:

Disk /dev/sdb: 7814037167 sectors, 3.6 TiB
Model: BUP BK          
Sector size (logical/physical): 512/4096 bytes
Disk identifier (GUID): F33087C3-E03F-4A5A-A52A-2D5C30471082
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 7814037133
Partitions will be aligned on 8-sector boundaries
Total free space is 3692 sectors (1.8 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              34          262177   128.0 MiB   0C01  Microsoft reserved ...
   2          264192      7814035455   3.6 TiB     0700  Basic data partition

I tried the following:

1. sudo gdisk /dev/sdb followed by the v command which resulted in the following:

Command (? for help): v

Problem: The secondary header's self-pointer indicates that it doesn't reside
at the end of the disk. If you've added a disk to a RAID array, use the 'e'
option on the experts' menu to adjust the secondary header's and partition
table's locations.

Problem: main GPT header's current LBA pointer (1) doesn't
match the backup GPT header's alternate LBA pointer(7814037166).

Problem: main GPT header's backup LBA pointer (7814037166) doesn't
match the backup GPT header's current LBA pointer (1).
The 'e' option on the experts' menu may fix this problem.

Problem: The backup partition table overlaps the backup header.
Using 'e' on the experts' menu may fix this problem.

Caution: Partition 1 doesn't begin on a 8-sector boundary. This may
result in degraded performance on some modern (2009 and later) hard disks.

Consult http://www.ibm.com/developerworks/linux/library/l-4kb-sector-disks/
for information on disk alignment.

Identified 4 problems!

2. I used gdisk e command as instructed to try and fix that, but when I close and open gdisk and enter the v command I get the same result.

3. I tried to write (w) the table to the disk, but that also didn’t work.

4. I ran the disk error checking option (in the harddrive properties) in Windows 10 and it resulted in no errors.

I am a little lost as to what do, any help would be greatly appreciated.

PS: I am new to Linux so bear with me :), and let me know if any other info is needed.

Edit1: As per the comment by @oldfred , I performed the following gdisk commands on the drive (x -> e -> w) and restarted the pc. Now the

The backup GPT table is corrupt….

message doesn’t show on sfdisk -l and 3 of the problems shown by gdisk’ v command are gone, but when I open GParted, I still get the

The backup GPT table is corrupt….

message.
Result of sudo sfdisk -l /dev/sdb

Disk /dev/sdb: 3,65 TiB, 4000787029504 bytes, 7814037167 sectors
Disk model: BUP BK          
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: F33087C3-E03F-4A5A-A52A-2D5C30471082

Device      Start        End    Sectors  Size Type
/dev/sdb1      34     262177     262144  128M Microsoft reserved
/dev/sdb2  264192 7814035455 7813771264  3,7T Microsoft basic data

Partition 1 does not start on physical sector boundary.

Result of gdisk v command

Problem: main GPT header's current LBA pointer (1) doesn't
match the backup GPT header's alternate LBA pointer(7814037166).

Caution: Partition 1 doesn't begin on a 8-sector boundary. This may
result in degraded performance on some modern (2009 and later) hard disks.

Consult http://www.ibm.com/developerworks/linux/library/l-4kb-sector-disks/
for information on disk alignment.

Identified 1 problems!