Images you are using have different high/width ratio, each of them will behave differently depending on container size.
The simplest solution is - if you want all the images to be same size, make all the images same size.
If you want to avoid editing images you could just try to define image sizes:
.project-tile img {
width: 100%;
height: 80%;
}
This will work, but some images will be stretched to fit the container.
If you want to avoid stretching images you could define their behavior using object-fit: cover, but then some parts of images will be cut off. Or try some other object-fit options.
(I am not sure if object-fit will work without creating separate image containers within image-tiles).
The answer to your question depends on how do you want the images of different sizes behave in same size containers.