I'm working on these trees and when I join the the two parts the do this: Does someone knows why this happen or how to solve it? Meshes haven't modifiers at all.
EDIT: I have noted, When I join the meshes it became a mesh with two materials. And faound this same problem when using more than one material in a mesh in other case.
Video SHowing the issue: https://drive.google.com/open?id=1vkm1s97pM9xOuRF5J981CwfwyxQT-GTd
Thanks!!