The problem posed below is motivated by this problem of Chris Heunen and in fact is its reformulation in the language of usco maps. Let us recal that an *usco map* is an upper semicontinuous compact-valued map.

Problem S.Does each usco map $\Phi:M\multimap K$ from a compact metrizable space $M$ to a compact Hausdorff space $K$ admit a Borel selection?

Looking at the literature I found a lot of results addressing this problem. For example the classical Kuratowski-Ryll-Nardzewski Theorem implies the affirmative answer to Problem S if $K$ is metrizable. By Hansell, Jayne and Talagrand (1985), the answer to Problem S is affirmative if $K$ is fragmenable. On the other hand, by the result of Graf or Cascales-Kadets-Rodrigues, every usco map $\Phi:P\multimap K$ from a Polish space $P$ to a compact Hausdorff space $K$ has a universally measurable selection.

But to my surprise looking through the literature I cound not find an answer to Problem S (or I overlooked something?). All existing results imposing some restrictions on $K$ (like being fragmentable or linearly ordered) suggest that one should expect a counterexample. And indeed, there exists a counterexample under $\neg CH$:

Example.There exists an usco map $\Phi:[0,1]^2\multimap K$ to some Hausdorff compact space $K$ (namely, the square of split interval), which has a Borel selection if and only if the Continuum Hypothesis holds.

But what about a ZFC-counterexample to Problem S? What is known in this respect? Is the above Example known to specialists in the field?