Hello everyone. We have a situation where Sales orders' "Next Bill Date" is either getting reset or getting default to date of the sales order.  Sales order has Project with billing type of Charge-based billing (no Project billing schedule) and the lines of Sales order has mixture of non inventory items WITH billing schedule and service items.

Initial invoice gets successfully generated via Next Bill button but for some reason, the Next bill date after that gets reset to the date of sales order. 

We have all the accounting preferences set so that sales order CAN be billed without fulfillment.