Billing Schedules at Line Item Level

I have a sales order on which I have an item at $12,000 and a 12 month billing schedule. When I invoice it, click Next Bill, it correctly creates an invoice for $1000.00. But when I add an item to the same sales order without a billing schedule, labor in this case, and create the Next Bill, the system ignores the item with the billing schedule and simply creates the invoice for the labor item.

After much testing I have concluded that I cannot have items on a sales order with billing shcedules mixed with items without billing schedules. Also, I have tried two items on a sales order with different billing schedules and this also does not work.