Involutive Yang-Baxter groups never act as Frobenius groups

A conjecture of S. Ramírez states that every indecomposable non-degenerate involutive set-theoretic solution to the Yang-Baxter equation with dihedral permutation group of order $2n$ has cardinality $2n$. The conjecture is verified for odd $n$ and disproved for even $n$. The proof for odd $n$ is obtained from the more general result that the permutation group of a finite solution never acts as a Frobenius group.