The presence of fillets in a model can cause problems for MultiZone, since arguably a fillet could be either a side face or a source face and the mesh quality in the corner could be problematic. Ideally, a fillet should be split in half, with one half going to the source face and the other half going to the side face.
In addition, inflation is generally recommended to improve the high angled elements that would be formed along the edge that is shared between the source and side faces. Inflation allows the mesh to transition away from the boundary and reduce the angle. See Figure 175: Fillets and Inflation.
Alternatively, the fillet could be removed by assigning the fillet to the side face through a virtual topology operation.
Refer to Meshing: Virtual Topology for more information.