Yes, pay attention to whether the object you’re trying to change is either fixed or hug in width and height, these settings are often overlooked by new designers and they are very important to get a good result.
If the text is set to fixed width and hug height, this means that when you type enough characters to fill the selection this will create a new text line and also broaden the selection accordingly.
I hope that solves the problem, if not, let me know and I’ll cover all other possible solutions.
Have a great day and best of luck!