I am having an issue rounding images in a gallery. Previously, I've set the height and width of an image to the same value and then set the border radius to Self.Width/2 and this has produced a rounded image. However, I'm doing that today and the image has rounded corners but isn't a circle:

When I add a border to the image though it is a circle but it's as if the image isn't filling that circle:

Has anyone come across this recently, and is there something I need to change to get the actual image to appear as a circle? The above happens regardless of the image that is used. I've also tried changing the image position setting (fit, fill etc) but this doesn't help.
Thanks in advance for your help.