I recently encountered this issue. I have two volume(bodies) side by side, I want to mesh both and merge them together. I imprinted/merged all volume before meshing each body individually. After meshing them, I also imprint/merge both bodies just to make sure that they merged. There was no error message when I did that.
Then, I checked the coincident nodes and faces, these two bodies have a coincident faces with nodes on them being coincident. I thought that merging will take care of this.
What I want is two meshed bodies with a merged (shared) face; and nodes on that face are shared.
See attachment for pictures.