Responsibilities of a Power of Attorney?

The person holding a POA for my great-aunt is haphazard in taking care of the financial responsibilities. Recently, the IRS garnished her accounts for back taxes due. There is plenty of money in her accounts. A CPA calculated the amount due, he just failed to pay.

I am considering challenging the POA assignment (great-auntie has documented dementia). In the meantime, can these types of fines be charged against the POA's share after the death of my great-aunt? Should the heirs consider/demand an audit?