Custom Image Links Switching

Hi there! I am designing a page of my site with multiple images that link to different pages. However, every time that I put a custom URL on one image, the custom URL on another switches.

For example:
I want it to be
image a = abc.com
image b = def.com
image c = hij.com

but instead I get
image a = abc.com
image b = abc.com
image c = def.com

Is there any way to fix this?