When entering the tracking information when the invoice number contains spaces, the following error occurs (either via UI or API) "An error has occurred".

To simulate or perform the analysis of this scenario, just:

1. Insert an invoice (via API) to an order with spaces in the invoice number (make sure that the invoice doesn't contain any tracking information);
2. Add tracking information via UI or API:
3. Notice that you receive an error code 500 along with the "An error has occurred" message.

For orders that are already invoiced with the space, and tracking is informed later, unfortunately there is no way to enter tracking data. However, to avoid this type of issue, the ideal is not to send space on the invoice, or inform the tracking data when inserting the invoice.