while scaling images in Premiere the uniform scale is not working even though it is checked. the images are being stretched vertically but not horizontally.

While scaling images in Premiere the uniform scale is not working even though it is checked. The images are being stretched vertically but not horizontally. I have never had this problem before and have three instances from others with the same problem. I have found that if I snip the picture from the screen I can scale with no problems but the original photos on the timeline will stretch and be disordinate.