On your 1st screenshot with “Rental Unit Details” screen selected, you can clearly see that there is “No Linked Data” to this screen.
This is the only reason why you can’t access the image (and other details about rental unit).
So, it seems that you’ve set up the connection from “Rental Units List” to “Rental Unit Details” screen incorrectly.
I guess that on Rental Units List screen you use a simple list. Did you set up the connection there? Or in some other place?
Add an action to this list to Link to the details screen, remove previous connection and all should work fine.
Best regards, Victor.