Twilight Princess repeatedly crashing emulator "Unknown opcode"

[DjBlades]

Heyo everyone, I've been playing through Twilight Princess, but suddenly it's began crashing after I changed a few things.
Using a hex editor, I changed the region of my save from PAL to NTSC-U, mainly so I could make use of the american version's AR codes.
I enabled 3x Enemy damage and 2x enemy health. The game played fine for a while, then completely froze throwing an error offering Abort, Retry or Ignore. If I manage to get rid of it, Dolphin itself throws an error, which I've attached to the post. I disabled Dual-core as suggested, but this still happened.
I found that this happened every time I killed one of the plant enemies, so I disabled the 2x enemy health AR code and everything worked fine for a full hour, no problems (aside from quite a few stutters, but I imagine that was the result of disabling dual core). But then eventually the game crashed again, this time from attacking a set of barrels while in wolf form. Exact same error.
I'd rather not disable the enemy damage AR code, is there any easier way for me to narrow down the potential causes?

Specs:
OS - Windows 7
RAM - 8GB
GPU - Geforce GTX 770
CPU - Intel i5 3570k
Emu Version: 5.0-1528, changed to 5.0-2087 after problem began.

[JMC47]

It's probably the action replay codes at this point...

[DjBlades]

Does that mean it's likely a bad code, or that I wouldn't be able to use them at all? Twilight is disappointingly easy and I was hoping the codes could give it a decent challenge.