New Checkout | Problem With Merge Username & Lastname

In version 4.11.2 I have a problem with the new checkout system. The problem arises during the ordering process. There are some orders that store half the names. And that creates a big problem for orders. But the strange thing is that he doesn't do it in all orders. And the strangest thing is that no matter how many tests I have done, this has not happened to me in any of my orders.
However, I have a large number of orders where the name and surname have half the characters.
In the new checkout I have activated both fields but by default it displays them in a large field. It merges the fields and obviously somewhere there creates the problem.
Does anyone have any idea how to fix it?