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We attempt to clarify several aspects concerning the recently presentedfour-dimensional Einstein-Gauss-Bonnet gravity. We argue that the limitingprocedure outlined in [Phys. Rev. Lett. 124, 081301 (2020)] generally involvesill-defined terms in the four dimensional field equations. Potential ways tocircumvent this issue are discussed, alongside some remarks regarding specificsolutions of the theory. We prove that, although linear perturbations are wellbehaved around maximally symmetric backgrounds, the equations for second-orderperturbations are ill-defined even around a Minkowskian background.Additionally, we perform a detailed analysis of the spherically symmetricsolutions, and find that the central curvature singularity can be reachedwithin a finite proper time.

Inconsistencies in four-dimensional Einstein-Gauss-Bonnet gravity