Is Person Source not editable once it's populated?

Hello, 

I have scoured over the product documentation and the community posts and I could not find anything to tell me one way or another. I'm really hoping one of you awesome users has the answer! In the past we have had all of our website form fills populate person source as website no matter how that person found that website page. We are now making a change and doing more advertising so we want to set person source as Paid Google Ads IF the person came to the page with a UTM from one of our campaigns. 

This process has taken some trial and error, but I think I have it working for any new inbound leads. I'm working on making a nice report though and was hoping to update the person source on some records so my report is accurate. Is there a way to change the person source on a record? 

Here is what I've tried: 

• Manually typing in the correct value on the person info tab from the database but it doesn't save. 
• I created a smart campaign to find all the records I wanted to update. Then ran a batch campaign to update the field. 

Any other ideas or will I just have to wait this out and manually update the report?  

Thanks!