Thank you for your post!
Please provide some additional information:
-What exact Operating System are you on? (Windows 7 Pro, Windows 10 Home, etc)
-What exact version of FileMaker are you running? (ex. FileMaker Pro 16.0.2)
-How are you creating the New Window? (via script, via Menu: Window > New Window, etc)
-Does this issue occur in a New File?
-Does this issue occur on other machines?
I look forward to your response!