Underpayment from Estate

[Anachronism]

I finally received the payment from my fathers estate. The amount I received was 10k less than agreed on the Estate Accounts. When I questioned the solicitor she accepted this was her mistake yet refuses to reimburse me until she receives the money from my sister who was overpaid the same amount and is apparently unable to send the funds for another five weeks. In her words "I cannot transfer sums out of our client account as this would be in breach of Solicitor Accounting Rules. I will collect the monies and ensure you receive interest on the underpayment."

Is she liable or am I at the mercy of my sister paying which given previous form is highly unlikely?

[des8]

Was the solicitor the executor of the will, or just acting on the executors instructions?

In any event it was the solicitor's error, and if your sister does not repay them, they would not transfer monies from their client account to you.
However they will be covered by Professional Indemnity insurance of upto at least £2,000,000 (unless minimum limit has increased since I last looked)
and all they will need to do is to make a claim on their insurers.

I doubt there is anything to be done immediately.
It would be regarded as unreasonable not to allow them time to correct the error by recalling the overpayment to your sister, especially as they have stated you will receive interest on the amount owing.