HDL to 'correct' data in the first assignment

Summary:

I wish to correct the location code in the first assignment record created when the employee was hired. I am using the effective start date in the load file which matches the hire date, I've tried it with the Action code and without but am still getting an error message.

I suspect it might be something to do with the EffectiveSequence and/or the EffectiveLatestChange but just not sure.

Can someone please help me to understand what I need to do, and why?

Content (required):

The below is the load file I am trying (in the code snippet section).