The geometry preparation or "cleaning" is an important key to produce a good finite element model, so take your time to properly cleanup your geometry before starting mesh.
I mentioned that gaps exist between several curves in your model and this will lead to nodes mismatch.
Don't hesitate to use the geometry / surface / non manifold add to ensure that all yellow highlighted curves are presenting your desired free edges before meshing. You can also split your geometry (surfaces) in order to match the several parts edges.
look at these videos :
Hope this helps,
I'm sure I'm missing something, when I use Unrefine, it doesn't remove the
boundary between the elements (doesn't merge them together), it's just
making all the selected elements flattened (maybe bringing them down to a
specific height,...)!, please see the snapshots below and let me know if
you have any comments.
[image: Inline image 1][image: Inline image 3][image: Inline image 2]