Translation-groupoid representation conjecture for orbifold groupoids

An orbifold groupoid is a Lie groupoid presenting an orbifold, and a translation groupoid is a groupoid of the form $[G\ltimes M]$ arising from a smooth action of a Lie group $G$ on a manifold $M$. The action is locally free when every isotropy group $G_p$ is discrete.

Translation-groupoid representation conjecture. Every orbifold groupoid can be represented by a translation groupoid with locally free group action.

The converse to the construction of an orbifold groupoid from a locally free compact Lie group action remains open in general. It was partially proved for effective orbifold groupoids.