player/npc model submesh blending with main body mesh issues

while working on gui and using the offline client mode,
didnt noticed until i used this standalone feature of the client,
multiverseclient.exe --standalone --use_default_repository

the demo world shows npcs equipped with their submesh armours,
but noticed that submeshes blend/merge together with the main npc or player body meshes, and looks like flickering.

any particular reason why this happens? and is there a workaround to it?