I checked and I saw that your code creates the fields by getting the $loop variable value, meaning that the field's ID on the product is like this "variable_early_bird_expired_date_0" and it is saving only "variable_early_bird_expired_date" as a custom field.
This case requires some custom coding and this falls out of the scope of this support forum, we can't provide custom coding/development.
What we can help with is:
you'll need to change your code in order for it to save the custom fields like "variable_early_bird_expired_date_0", "variable_early_bird_expired_date_1" etc. in order to properly set them on the product page and be able to lock the fields on the translations.