SCRIPT ERROR ON OPCODE 1641

Prior to this error I was going to follow the spy to the location. He was just running against a river northeast of Sargoth. He was just south of the first bridge that crosses over the forked rivers that go into the ocean. (Just for arugments sake, I left him alone for like a month. Came back and he was still humping the river.


Game Version 1.011
This is the in-game error I get.

SCRIPT ERROR ON OPCODE 1641: Invalid Party ID: 102050592; LINE NO:51:
At Game Triggers trigger no:12 conditions.
At Game Triggers trigger no:12 conditions.

Heres also a screenshot of it.

Did it occur when he started to run, or when you attacked him?

When I came into his line of sight. Just before I attacked him.