Complexity for five monotone agents

Determine the computational complexity of contiguous envy-free cake cutting for general monotone valuations when there are five agents.

Background

The paper contrasts its PPAD-completeness result for additive piecewise-constant valuations with prior results for general monotone valuations. It reports an efficient algorithm for four monotone agents and PPAD-hardness for non-monotone valuations, but the corresponding complexity for five monotone agents has not been settled.