The double surface issue has been reported by several people, https://github.com/NREL/legacy-openstudio/issues/3. I believe it has to do with changes made to SketchUp's observers in SketchUp 2016.
The Legacy OpenStudio Plug-in has not been officially supported by DOE for several years. We have been providing minimal updates to the Legacy OpenStudio Plug-in to update to each EnergyPlus version on a volunteer basis. However, significant changes (new features or bugs such as this) are harder to make on a volunteer basis. We are aware of this issue, have some ideas about its cause, and do want to fix it but canâ??t make any promises on the timeline. We would welcome and help any other parties that are willing look into this bug. The long term goal for the Legacy OpenStudio Plug-in is to be a self-sufficient project with its own volunteer development community.
On the other hand, the new OpenStudio platform is well supported by DOE and several other entities. If it has been a while since you last took a look at the new OpenStudio platform I'd invite you to look again. With the Commercial Reference buildings available in OSM format, a new parametric tool on the way, and tons more HVAC support you might find that the new OpenStudio platform could work for your needs.