On no, always something going on I don't really have any advice... but it's possible that Willow is just slacking cos she's not watched as carefully anymore. I basically potty trained Alice in less than two weeks but when she's alone she takes chances, or if she's somewhere she's not used to be at.
There must be something going on with Walter, I can't imagine a dog being snappy like that for no reason Frasier snapped at my husband a couple of times, especially if he was in the car... but Frasier was abused by a man so that's understandable in a way. He used to act crazy with me too but it was more of a dominance thing.
My Jack Russel from back in the days used to go mental if he slept on my bed and I accidentally pushed him in my sleep. It was scary but he never bit, just flew up and barked, they reason why I don't know...
The only time my dogs have snapped at their butt is if they got a flea bite... but it's winter by you so that can't be. And he just had his glands checked... and I assume the doesn't have worms bothering him either, or any poop problem like constipation?
What does the vet think it is?