i get this warning along with overconstrained checks for several internal nodes when running analysis for model having C3D8RH elements with 3 layers of shell homogeneous sections S4R elements embedded in the matrix also the model had periodic boundary conditions.

but i dont get any such warning if i run analysis for homogeneous solid with PBC condition having C3D20R TET elements

what can be the possible reason ?

i think problem due to using hybrid element which i cant neglect !!