When using for a checkbox field in lightning-record-edit-form, the field can only be saved once. Other fields can be changed and saved more than once. NOTE: a custom checkbox field on Contact was used in the testing.
Steps To Reproduce: Add a lightning-input-field for a checkbox field in lightning-record-edit-form for the above recordEditFormDynamicContact component.
For example, I have custom field on Contact called MarketablePerson__c.
<lightning-input-field field-name="MarketablePerson__c" ></lightning-input-field>
Test saving the contact record by changing the checkbox field and clicking the Save button. Don't refresh the page. Just verify the results with a SOQL query. Change the field again, click the Save button and verify the field was not saved.