That’s about the right size, but the official AVCHD release from Harmy is divided up into 17 rars, each being about 500 mb except for the last one.
The fact that your copy came from one big rar means someone extracted and re-archived it, perhaps unintentionally introducing some glitches along the way.
I hate to say that you should start over, but if you can’t get what you have to work, I would highly recommend that you try using the official multi-rar links found in this guide:
Added bonus- since they are in smaller pieces, you don’t have to download them all at once.
Edit: You beat me to it!