Hi Bejamin,
I also struggled with this TextArea field concept. For this type in particular, you must know it is not a simple string: it comes in the form of:
{'format': 'html', 'content': 'Description of incident'}
So if you want to change the text of the field, you must use the "content" part, like this:
incident.description.content = "new description of incident"
HTH
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Pierre Dufresne
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