Custom field data keeps getting deleted upon saving in admin

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(This is somewhat related to the other topic I had posted earlier here, although this issue is different.)

I needed to add a new tab to one of my page templates to have some custom fields. I’m running into an issue where Grav seems to be deleting some of my data after saving when the uploaded file form already has data saved and the select box also has data saved.

The odd thing is, I can save both again and that works, but the moment you save again it deletes everything custom but the select dropdown’s data. Oddly Expert mode doesn’t do this.

Code is below from my blueprint file:

title: Review

'@extends':
    type: default
    context: blueprints://pages

form:
    fields:
        tabs:
            fields:
                review: 
                    type: tab
                    title: Review
                    
                    fields:
                        review_basics:
                            type: section
                            title: Basics
                            underline: true
                        
                        header.review_basics_masthead:
                            type: file
                            label: Masthead
                            destination: 'uploads/reviews'
                            blueprint: 'themes.mytheme'
                            accept:
                                - image/jpeg
                        
                        header.review_basics_author:
                            type: select
                            classes: fancy
                            size: long
                            label: Author
                            options:
                                'Author 1': "Author 1"
                                'Author 2': "Author 2"
                                'Author 3': "Author 3"