https://github.com/kwsch/PKHeX/blob/754b87a4f09b2aa5718e205e55d8d41722c498d7/PKHeX.Core/Saves/SAV6.cs
Sav6 offsets.
Specifically, these are the block offsets in an XY save.
So let's say you want suspect the Trainer1 block to be the bad block, you can import it in by copying the data over from a fresh save, using a hex editor.
I'll be using the program called HxD for this.
So I loaded the save into HxD, now to select the range.
For example, if I'm selecting the Trainer1 block, it should be from 0x1400 (as per shown above) to 0x17FF (0x1800, the next block, and minus by 1).
You can Ctrl+E to select block (in HxD), then indicate the area.
Now, the prompt will close after you select OK. Double check you selected the right area.
Copy the data. (Ctrl+C)
Now, go to the other save, and go to the same location and place your cursor there.
In this example, it'll be 0x1400.
To go to that location, you can Ctrl+G and type in the value.
Once you're at the location, you can Paste write (Ctrl+B)
Once done, export the file from HxD.
Then load that edited file into PKHeX. Then export it from PKHeX. (this is to fix checksums).
Now check it in the game, see if it loads. If not, rinse and repeat for each block.
I recommend doing half of the entire save, then keep halving.