[2.0.0-beta5] FieldFormatterSource: some settings are not saved

Problem/Motivation

Fresh Drupal 11.0 install, ui_suite_dsfr theme.

On Layout Builder:

1. I add a field using "Component per item" field formatter
2. I pick a component
3. In a slot, I add a FieldFormatterSource and configure it
4. I save
5. I reopen the field formatter configuration
6. Sometimes, my FieldFormatterSource configuration has not been saved

The issue happens with:

• Enttity Reference / Label / Link label to the referenced entity (a checkbox)

The issue doesn't happen with:

• String / Plain text / Link to the Content (a checkbox)
• Enttity Reference / Rendered entity / View mode (a select)
• Boolean / Boolean / Output format (a select)
• Datetime / Time ago / Future format (a textfield)

Proposed resolution

What's wrong with this specific field formatter ? The issue happens in all entity reference fields tested.