When I have two custom field types, the menu sort order doesn't behave as expected.
In the screenshot below, I have set:
Post Type for "Portfolio Reflections" has Visibility > Menu Position as 1.
Post Type for "Teaching Resources" has Visibility > Menu Position as 2.

When I have two custom field types, the menu sort order doesn't behave as expected.
In the screenshot below, I have set:
Post Type for "Portfolio Reflections" has Visibility > Menu Position as 1.
Post Type for "Teaching Resources" has Visibility > Menu Position as 2.