Our client, an 8-year old girl, also got slapped several times and had some bad scratches from its claws. The scratches seemed to "infect" her with a desire for sugar, similar to that of the monster itself. You see, infallibly it was attracted by bowls of sugar and candy that we used for bait for our observations. After the worst incident our client was attracted to the bait with a frightening fervor.
She is much better now and only eats sweets on Saturdays, but very fast.
(I believe I might have been "infected" too. I used to take one spoonful of sugar in my coffee, now I crave at least 6.)
After two weeks of almost nightly visitations the monster stopped coming.
We don't know what made it appear or disappear.
If you know anything about a monster like the Gutrotter please let me know, any information can be valuable.