Toggle Pixel Aspect Ration Correction

Check the settings of the Preview codec in the sequence settings.

To correct the aspect ratio of your video:

1. Select the clip in the Project panel.
2. Go to Clip > Modify > Interpret Footage.
3. Under Pixel Aspect Ratio, choose Conform to and select the correct aspect ratio for your clip.

For more detailed information, you can refer to this guide: Correct Aspect Ratios in Premiere Pro.

Cheers,
Paul