Circular Dependency?

Hello,

I have a Customers table that’s linked to a Transactions Table and am using Direct Query mode.

I’ve created a calculated column on the customers table that finds the date of the customer’s earliest sales order:

FirstSalesOrderDate =

    CALCULATE(

        MIN('Transactions'[Date]),

        'Transaction'[Type] = "Sales Order"

        && 'Transaction'[State] <> "Closed"

        && 'Transaction'[State] <> "Cancelled"

    )

This works as desired.

My problems occur when I try and add a second calculated column to the Customers table that returns a date with just the year and month from the FirstSalesOrderDate. EG: The date 2023-05-24 becomes 2023-05-01:

FirstSOMonthYear =

       DATE(YEAR([FirstSalesOrderDate]), MONTH([FirstSalesOrderDate]), 1)

This creates a circular dependency for some reason, yet FirstSalesOrderDate in no way references FirstSOMonthYear.

I’ve also tried changing the calculated column FirstSOMonthYear to this:

firstSOMonthYear =

 VAR theDate = CALCULATE(

        MIN('Transaction Header'[Date]),

        'Transaction Header'[Type] = "Sales Order"

        && 'Transaction Header'[State] <> "Closed"

        && 'Transaction Header'[State] <> "Cancelled"

    )

RETURN DATE(YEAR(theDate), MONTH(theDate), 1)

This too results in a circular dependency, yet it in no way references the first calculated column.

What I want to know is why I’m seeing this behaviour, and what I can do to avoid it.
Can anyone help please?