The only thing that comes to my mind is Yunas vomit.... After the first few days it became dark green and smelled of liquid poo. In her case it was due to an obstruction... She is not a toy swallower either...
However the vets did not think it was an obstruction. Tested her for everything. Had X-rays done. After two weeks I finally told them she needed exploratory surgery. Luckily my regular vet was back... Was dealing with the other vets in the practice. He agreed to the surgery but still he did not think she had an obstruction either. Her X-rays were clear.
She did!!!! I am not sure if any if this will help, but with Shys symptoms I would certainly keep the possibility in mind.
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