Custom 'Create a Record' action on a related list shows different page layout in Lightning Experience

When you create a custom 'Create a Record' action in Salesforce Lightning Experience and add it to both the "Mobile and Lightning Experience Actions" section of a page layout and to the corresponding related list, the action may display different fields depending on where it is clicked.

• When clicked from the highlights panel, the action shows the fields defined in the action's own page layout.
• When clicked from the related list, the action shows different fields — specifically, the fields from the page layout associated with the record type, rather than the action's own layout.

Example scenario: In Object A, you create a 'Create a Record' action that creates Object B records, specifying a particular record type and a custom set of fields. The action is added to both the Mobile and Lightning Experience Actions section and to the Object B related list on Object A's page layout. When users click the action from the related list, the fields displayed do not match what was configured in the action layout.