Multiple values embed Loses Additional Values on Re-save

Problem/Motivation

When I first save a configuration with multiple values (for example, three items), the form correctly displays all the values.
However, if I later edit the embed and re-save—even without making any changes—the form saves only the first value, and the additional values disappear.

Steps to reproduce

Install the latest version of the module along with the Embedded Content Examples module.
Configure an instance of the "StyledList" embed with multiple values (e.g., three items).
Save the configuration; all values are displayed correctly.
Edit the embed and re-save the form without modifying any values.
Observe that only the first value is retained, while the others are lost.