Hi, I'm Bhavik. Welcome to JustAnswer. I'm reviewing your question now, and will reply back ASAP.
Please tell me the model of your TV.
Please try below steps :-
Okay, When you are going back to previous channel , Do you see your previous settings ?
Okay. Please try above settings one more time and after doing this setting do not change channel. Just turn off your TV and restart setup box and see if it is saving your settings.
Okay. We need to change the default setting. Give me sometime. I will get back to you on this.
it should not take much time.
Please try and see if below settings works for you. This has worked for other users :-
Press MENU and open the Picture MENU
Highlight THEATER SETTINGS and press ENTER
In the Auto Aspect Ratio field, select OFF
Press DONE and press ENTER on the remote.
Do you have C button on your remote ? If so , Press the C button on your remote to save your changes.
Also you need to change this setting as well :-
Okay, May be it is not there for your model.
Any luck after changing Auto HD setting ?
Alright . Let me know the end result.
You are welcome !!