If field is disabled on form display data is lost

Problem/Motivation

I'm working on a content type with different form displays. One specifically for workflow. When using a form display that doesn't include a field that has image_field_caption the caption data is lost.

Steps to reproduce

Save an entity with image_field_caption data. Update the form display and move the field that has caption data to disabled. Now edit and save the entity again. The data is lost.

Proposed resolution

When testing I noticed that the code checks for $value['image_field_caption']['value']. That is not available when the field is disabled because it is attached to the field widget. But $value['caption'] and $value['caption_format'] look like they are still there.

Remaining tasks

Come up with a proper solution.