HTML Snippet - Image Size Issue

HTML Snippet - Image Size Issue

I have placed a .png image in an HTML snippet on a page. Sometimes the image shows in it's full size when the page is loaded, however, it sometimes shows on only half the image and a scroll option appears on the right side of the panel. Once the page is refreshed, it usually shows full size again without the scroll option. Any way to force the image to show full size consistently when the page is loaded?