I am having trouble separating the limbs of my R6 rig in Blender. I am in update 2.8, if that affects anything, because I have done it in 2.7 with ease. Here is a short gif of the problem I have approached. Selecting different vertices does not effect anything to my knowledge.
I myself imported a rig and tried to take it apart. I tried separating the right arm and the left leg but it seems that when you are selecting a limb, there are connection to different parts of the bodies that stay with the selected part. This would result in the problem you are experiencing which is making those vertices or connections stretched and longer. I think in Blender 2.8 it’s a different way of making the connections since it was easy to do this in Blender 2.7. I can’t say for certain this is correct, but in my opinion it seems this way from my experience and from from your GIF. (Don’t mind the wrong names of whatever those dots are since I do not model or user blender often)
Hover over a vertex of the arm and press L, this selects everything that is connected to that vertex. If this doesn’t work, then probably there are overlapping vertices. You could also try selecting a bunch of vertices that is part of the arm and hit Ctrl and the plus sign (+) to select the connecting vertices until all of the separate part is selected.
Hi, I was experiencing this same issue. Basically what I found to work was I just followed this tutorial Blender rig tutorial
I downloaded the blender file in the desc, exported my character then loaded the texture file from the exports onto the material then I exported the hats separately and made them children of the hat attachment part of the rig.