The data looks correct, the question is why? The only thing that I can think of is that the field key reference is wrong.
After your code updates the field, what is the field key reference? Look at the meta key for the same post, you are looking for the one that has the same name but starts with an underscore. The value of this field will be something like “field_7777777”. Does this field key match the field key of the field you’re updating? Does this change when you re-updated the field by updating the post in the admin?
