A family of Microsoft word processing software products for creating web, email, and print documents.
Does the text box size reduce only in this particular file or all the files which contain text boxes?
Do you have any other issues while printing?
Try the same in other Office applications like Excel, Power point and check.
Try to print in application safe:
Open run window (Windows key + R) copy and paste the below line and click ok to open in safe mode.
Winword /safe
Create a text box and try to print and verify the status. If dimension comes correctly disable add-ins from File> Options> Add-ins and verify the issue.
If you face the same issue in safe mode; change default printer and check with printing.