System Information
Operating system: Windows 10 Pro 1803
Graphics card: GTX 1050Ti

Blender Version
2.80 (sub 37), branch: blender2.8, commit date: 2018-12-11 23:04, hash: ff108aac631, type: Release
build date: 11/12/2018, 15:11

Short description of error
Multiresolution modifier: Switching between Simple and Catmull-Clark and back deforms mesh.

Exact steps for others to reproduce the error

1. Delete default cube
2. Add -> Mesh -> Monkey
3. Switch to sculpting tab
4. Add Multiresolution modifier. Catmull-Clark is already selected.
5. Subdivide a couple of times.
6. Switch from Catmull-Clark to "Simple".
7. Mesh is already deformed at this point but may be hard to notice depending on the mesh, more noticeable with meshes with more concave parts.
   
8. At this point both of these result in deformed mesh:
   1. After switching to simple, click subdivide again. At best holes appear everywhere in the mesh or it goes completely haywire.
      
   2. Switch back to Catmull-Clark without doing anything. Deformation is less intense but deformed nonetheless.
      
9. After that switching back and forth between Catmull-Clark and Simple, or subdividing in any mode intensifies the deformation.