"The dog sits beside the child" should also be an acceptable answer. 10/17/17
Don't forget to submit it as a report when you encounter it again. It'll have a higher chance of being noticed.
It is now accepted, but "The dog sits by the child." is not yet accepted 1/8/18
I encountered this again just now, I placed "The dog sits beside the child" and it was still wrong...
As of 12/03/17 1:21 pm KST "The dog sits beside the child" is already accepted
Aww. Such a tranquil moment after all the exploding balls, hurled furniture, etc.