Most likely you have an issue with your images declared dimensions. Here, they’re set to 100% width and height, that’s why the ratio breaks.
So they do that because you told them to do so 
Modify dimensions in your images properties.
It would be easier to guide you if you can share your project’s url (Check here on how to do this : How to Enable a Webflow Share Link - Webflow Tips - Forum | Webflow )