Another wiki describing the term:

https://wikispooks.com/wiki/Parallel_Construction

And another related concept: https://en.wikipedia.org/wiki/Cargo_cult

One entity provides advice, a different one applies it.

Cargo cult: The advice is applied incorrectly.

Carrot problem: The advice is provided incorrectly.

How to distinguish the two, without understanding the details? Looking at what worked doesn't help. Checking the motivation for providing the advice is asymmetric. Any other ideas?

That is something different. There is no deceit or hidden information (well not necessarily). Where as a carrot problem needs there to be deceit and hidden information.

Yes there is, that's the whole point actually

“Sandbagging” fits better.