If a PR has breached their duties then it may be possible to take action against them. This can include:
an application to court for the removal of the PR
an application to Court for an order setting aside a transaction the PR entered into on behalf of the estate
an application to the Court for an order that a PR effectively repay any profits he has made at the expense of the beneficiaries
The PR has personal liability for any actions they undertake which are in breach of their duties and so if they have caused loss to the estate then they will have to pay that money back.