There are the steps to reproduce the issue:
1- Add two custom text fields for a product.
2- From the FO, add some text to the first text field, save it and add the product into the cart.
3- Add some other text to the first text field of the same product , save it and add it to the cart.
4- Add another product that does not have any custom field.
In the cart you have 2 products for the one having the custom text fields and only one for the other product.
In the BO, the order is divided into two ones:
- One with the 2 products having the custom text fields.
- Another order for the other product.