3702879 - Error "You must not change billingplanitemusage" encountered when using patch method in commercial project API

In the "Try Out" page of the API Commercial Project - Create, Update, for a customer project, when trying to change the existing billing plan item usage (e.g., from "Time and Expenses" to "Payment on Account"), receive the error message in the response: "You must not change BILLINGPLANITEMUSAGE". However, it is possible to manually change the billing plan item usage in the "Plan Customer Project" app.

SAP S/4HANA Cloud Public Edition

billingplanitemusage, patch method, commercial project api, plan customer projects app, error message, time and expenses, payment on account, api restriction, sales order item billing plan, field dependencies. , KBA , SD-SLS-PBS , Project-Based Services in Sales Documents , Problem