Hello, I'm TV Tech1 and I'll be working with you to identify and help you resolve your problem.
I had a customer that had that same problem before.
I think we had to reset the TV set to get that problem resolved.
To do that, get your Sony TV remote out. Sit down close to the TV set so you can touch the TV's power button. Press the volume button on your remote control and make sure the TV responds to the volume button. Once you see it appear, you know your TV set can read the remote control and you're close enough to press the power button.
Now...here's the Reset sequence.
Find the UP arrow you use on your remote control to navigate UP in your TV menues.
With the TV turned on, Press and HOLD it, then Press and release the Power on/off button on your TV set, not the remote.
The TV should shut off, and then turn itself back on.
That's the reset.
Now, you may have to access your network settings, and have to set the TV back up to communicate with your router to re-establish your network connection. You may need to also reconnect to Netflix with the username and password XXXXX
I don't expect you'll have to do the Reactivation sequence using both your TV and computer to generate a new activation code on the TV, but if you do, then perform the Deactivate devices and Reactivate Devices from your computer with the TV accessing Netflix.
That whole process I just listed should restore the screen size on your TV set with Netflix.
Give that a try. Reply back to me when you're finished.