[Lorraine]

Puppy with the broken neck probably fell off the grooming table or was in the grooming loop when it jumped off and that will break a neck. Yep you really do have to pick experience groomers, owner/operator are the best if you can find one.
As to the sudden potty training problems, I wonder if there may be bladder stones. I don't know if a urinalysis would always show up an infection if stones are present. An xray will show stones if they are there. My first Yorkie had stones at about 7 years of age and was difficult to diagnose until my second opinion Vet was suspicious of stones, ran an xray and poor little guy was packed with them.
They can be dissolved with certain prescription diets or in bad cases surgery may be required.
I would ask about that possibility and take her back or try another opinion.
Lorraine
Loriben Yorkies