You may occassionally experience issues with an image or images in the Instagram feed not displaying correctly, which can sometimes happen when Instagram expires content or if an image has not been cached correctly when the page was rendered.
First step is to re-save the page the Instagram feed is located on. This will purge the cache, including Instagram images, and should load again correctly after saving. Wait 30 seconds or so to ensure the cache has cleared and try refreshing the page.
If this still doesn't fix the issue, contact Roam Support and we can re-import your Instagram feed.