Steps to reproduce the issue

Preparing Child Fields

• Go to Content -> Fields
• Make sure you already have some custom fields created, one of these should be of type 'List', with a few options under "List Values"

Preparing Subform

• Create a new Subform field. Under "Fields" add any field you want, one of these should be the List field you created earlier.
• When creating the Subform field, go to the Options tab, and under the Form Options, set the Layout to 'Form'.

Replicating the issue

• Create a new article or edit an existing article.
• Edit the subform field in the article and add a few subform rows (even a couple is fine)
• Make sure to fill in the list child field for each row
• Now try to drag & drop a row up or down to re-order the rows

Expected result

You'd expect that all values in the child fields retain their value when re-ordering the rows.

Actual result

The values of the List child field get deleted upon re-ordering.

Here is a quick video showing the issue:
https://drive.google.com/file/d/1cr1LJejZSCsmXuzXw_vPe-HguPx9iZ6G/view?usp=sharing

System information (as much as possible)

Joomla 4.3.4

Additional comments

• This is not an issue when the Subform uses the 'Table' layout. This issue only happens when using the 'Form' layout.
• NB: The 'Form' layout can either be chosen manually in the Form Options, or it kicks in automatically when there are more than 4 sub fields.