Sawyer's mixed weak-type conjecture for two $A_1$ weights

Let $M$ be the Hardy–Littlewood maximal operator on $\mathbb{R}^n$, and let $u,v\in A_1$. Sawyer's mixed weak-type conjecture. There exists a dimensional constant $c_n$ such that

$$\Big\|\frac{M(fv)}{v}\Big\|_{L^{1,\infty}(uv)}\le c_n [u]_{A_1}[v]_{A_1}\|f\|_{L^1(uv)}.$$

This is the $A_1$-weight case of the mixed weak-type estimate discussed in the source and is attributed there to O. P. and R. The parser supplies no evidence that it has been resolved.