There are a lot of different directions the finger could ultimately point in...
The TMO as the client for the works would bare the final responsibility in some eyes but then they've probably appointed an independent PM to manage the whole project and procurement who you would expect to provide some guidance, a lot of times the client doesn't really have much of a clue of the detail they just know what they want as an end result and leave their appointed team to make it so.
Then you'll have the architects who would've most likely specified the desired cladding system, there will be some sign off on whatever product is proposed by the client but again they might not really have any knowledge of what's being offered and pick purely on aesthetics or costs whilst relying on the advice of their appointed team to make sure everything checks out. Some client's will have more control, their own in house specifications and guidelines which have to be following but it isn't always the case, hotel chains seem to be the most on the ball in this regard from my experience.
Then there's further consultants that the architect would've employed and relied on advice from, building control experts to make sure their proposals comply with local authority guidelines, fire consultants too for specific advice on fire safety and perhaps even facade consultants to give an overview that all elements of the works combine together to work as planned. You'd expect them to be employed anyway, there's always the potential that these parties aren't bought to the table at this stage and then responsibility would be passed on to the selected contractor to satisfy themselves that everything was designed as it should before starting work.
Eventually you get to the contractor(s) responsible for the works, your main contractor managing the whole project needs to be confident that the design works, that their bid is compliant with that design and then ultimately they're responsible for the installation adhering to that design, whether directly or via vetting of suitable subcontractors for different elements of the works.
Could be a big oversight by one party somewhere along the line or several small infringements by several parties that lead to a perfect storm.