[Backport to 10.1] Regression - Content blocks: validation invalidates all fields, instead of only the invalid fields

When a content blocks field contains multiple items and one of the elements doesn't validate, all items are marked as invalid (and get a red color/border).

Reproduction path:

• Install archetype with all essential components installed
• Configure content blocks on a document type
• select all available compounds
• save changes
• Edit a document with the content blocks field
• Add multiple entries and do not provide one of the required fields
• Save document
• Too many elements are marked as invalid

See screenshot with an example.