I found an issue with Merge All Faces in version 5A857.
When I do Solid > Solid Edit Tools > Faces > Merge All Faces on an object, artifacts are introduced that should not be there. Please see the video in which I illustrate this.
Merge All Faces.mov (11.8 MB)
When I use Merge Face instead this does not happen. And when I reinstalled version 5A855 this does not happen.
Am I doing something wrong, or is this a bug?