Glad to hear you are calling the vet in the morning
It's hard to say if this would be from the liver or something else as many health issues have similar symptoms. It could be the liver as he has had previous concerns, the symptoms also sound a bit like HyperThyroidism & the age is right for that.
As Taz is now a senior kitty be sure to ask for yearly urine tests & blood tests including T4 for thyroid issues, to make sure you are on top of any issues that may crop up.
Welcome to the forum
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for the appt, let us know what the vet says