I know nothing about Italian law, but I suspect that paying for a "professional" evaluation which is then "withdrawn" would be laywer-fodder in the US. At the very least, a refund of all monies paid. "Clients" relying on the report ... possible libel ... UoB's got deep pockets, I suspect.
I also know nothing about Italian law, but I suspect any possible liability would only go so far as the value of the contract. The contract will have been written (boiler plate) by UNIBO in the main part and of course they don't put themselves at legal/financial risk. This is just how these sorts of things work.
Notice that Rossi did not demand/suggest a re-test fixing the issues (which are only the ones that Levi chose to mention). Given that any such re-test would, I think, not be allowed by UNIBO with Levi operating solo again (or possibly involved at all), we all know that it isn't going to happen.