Data lost between pages when using default Id from URL

1.0 Problem/Motivation
The following is observed when a Contact Id is defaulted by using the query string ?cid1=nnn in the URL, or when Contact 2 is defaulted by a Relationship to Contact 1, which is defaulted from the URL. When creating a new Contact, or selecting the Contact from a select list on the Existing Contact field, it works correctly.

• If one makes a change to a field on Page 1, moves to Page 2, then uses the Previous button back to Page 1, the change is lost.
• If one make a change on Page 2, goes back to Page 1, and returns to Page 2, the change has been lost.
• If one selects a new or different Membership Type on Page 1, moves through Page 2, to Payment on Page 3, then the new Membership Type has been lost. If one goes from Page 1 straight to Payment on Page 2 it works OK.

2.0 Detailed steps to reproduce.
This is on Webform_CiviCRM 8.x-5.0-beta7, Webform 6.0.2, Drupal 8.9.14.
See the two sample webforms attached.

3.0 Proposed resolution
I note the existing Issue https://www.drupal.org/project/webform_civicrm/issues/3157032 → , but suspect that fix did not cover the case when the Contact Id is defaulted.