I doubt that this was an innocent failure on their part. There was a huge financial incentive for these firms to find some way to validate this project.
Successive foreign consultants warned about the risk of building this dam on water-soluble bedrock. The risk was not subtle.
The planning documents for this dam should be scrutinized very closely for evidence of omission or manipulation of data, and the firms involved should be investigated. And if they are found culpable, they should participate in the costs of shoring up the dam. They have played a part in this mess.