Recover data from a failed merge between two hard drive mounted on OS X with NTFS

I wanted to back up one Seagate HD onto another one (same model) and was using the software 'NTFS for Mac' by Paragon softwares to mount them both. However, in the middle of that process, the software failed and I had to unplug both HDs and replug them. When I went to check the orginial HD, it looks like it had been wiped from some of the data 😮, and as the backup did not finish, I have lost about 1.2 TB of precious files 😢....

Please tell me there is a way to recover this data?????

When I tried to 'repair' the volume with NTFS for Mac it said that the repair failed.

Any help will be greatly, greatly appreciated...