Lowest price not displayed (Price by attribute)

I have 2 carts, one (Zen Cart 1.3.7.1) and the other (Zen Cart 1.3.8a) that have the same problem.

With items whose base price is zero, and priced by attribute, the words "Starting at:" is displayed on the product info page, but the lowest price is not shown after that text as expected. How can this be corrected?

I was told that the solution to this is a selection on the lowest priced attribute, to mark it "base price".

Products using Priced by Attribute take the lowest price of each Option Name group of prices and combine them to make the Starting at price ...

Most of the time, just leaving all Attributes set to by included in the base price is correct ...

Only on occasion is it necessary to alter this and mark some attributes as not to be included in the base price ...