"Join as Shape" error when trying to import a file for shape keys from ZBrush This is my first time asking a question on this forum and I'm new to Blender, so hello everyone! This is pretty much my first time using ZBrush, Substance Painter, and Blender. Web searches got me a long way but I've hit a snag. There doesn't appear to be a solution online for my problem. The closest thing I found was another post on this site from over two years ago [link], but there wasn't a clear answer then. 

My workflow was: sculpting in ZBrush > Substance Painter > Blender. I exported an .obj from Blender back into ZBrush (I love its sculpting tools), and there I sculpted my desired shape key on a layer, split the parts and then exported it from ZBrush as an .obj. I imported it back into Blender and then tried the "Join as Shapes" function. Here are the results. It's not pretty... the mesh basically explodes. I tried applying transformations, but still no good. 

Here is a link to my project files. I hope someone has an answer!
Okay, so I found an answer. To reiterate, the problem was: I have an alien character with a frill (like the Dilophosaurus is Jurassic Park), and I wanted a shape key for the frill to go down. I made the original mesh in ZBrush. I exported it from ZBrush and imported it into Blender (after making texture maps in Substance Painter). I exported the mesh from Blender and imported it into ZBrush. After I adjusted the mesh so his frill was down, I exported it from ZBrush back into Blender. When I tried to do the "Join as Shapes" option, the error occurred. 

Now, the workaround: I imported the un-adjusted, frill-up version of the mesh from Blender into ZBrush, then I exported it right back into Blender without making any real changes. Now both the frill up and frill down versions are both exported from ZBrush (from Blender). Not sure why, but now "Join as Shapes" works, so I'm happy. Since the vertex count never changed, the texture maps I made in Substance Painter still work too. 

Thanks!