so erm, weird thing I found. I think its my codes but any help would be appreciated. When the scene has native bjs meshes and imported mesh, assigning custom material on all meshes works only on the native meshes. If I comment those out, the imported meshes get the custom material too.
PG repro here: https://www.babylonjs-playground.com/#UXCB15#59
comment out line 66 & 68 to see the difference. erm, what am I missing here ?