Wrong test used
In many trade contracts, where the specification of the product is important, buyers and sellers will often agree that the quality will be determined by an independent expert and that the expert's findings shall be "final and binding on both parties save for fraud or manifest error".
In one case, an independent expert was appointed to test an oil product. Part of his instructions was to use a specific testing method (method A) to determine the density of the product. The expert decided not to use the testing method A, but instead substituted a more modern method (method B), which was deemed to be more accurate.
The product was sold and a dispute arose regarding the specification. Although the expert had produced a report setting out his findings, these were not "final and binding" determinations because the method used did not comply with the contract. The buyers challenged the findings and what should have been a foregone conclusion became a protracted dispute. The seller was ultimately successful but sought to recover from irrecoverable legal costs from the expert who had not followed instructions.
Surveyors and other experts must ensure that they carry out instructions to the letter. If they intend to make changes they must obtain the customer's written authority to do so. If they do not then they are likely to face claims for losses caused by their failure to follow for instructions given.