Thanks for you feedback. Glad you like our game beside it's issues.
Concerning your playthrough, I'm sure there is no bug. To wash him just grab the sponge and hover it over the dragon longer, don't click. I also guess the mood of little dragon was low. He refuses everything under 25% mood. Try to raise mood first, by directly pet him after he slept as long as possible to reach mood 100%. Then wash him until 0% dirtyness. Always clean poop as fast as possible. Then you can feed him as you like.