I'm using Windows 10 & SW 2015 SP5.0 (I also see this w/ SW 2016).
I work with a Windows Explorer window open and extra large icons showing. In SolidWorks, "Show thumbnail graphics in Windows Explorer" is turned on. It worked fine in Windows 7.
I see a mess - some thumbnails correctly visible, some shown as icons. The green progress bar constantly runs through the address bar. Refreshing (using the refresh icon in the address bar, or using F5) usually fixes it (shows thumbnails), but not always all thumbnails. Sometimes repeated refreshes will show everything. But, they go away again as I continue to work in SolidWorks.
I've had my reseller look at this - we've reregistered DLL's. I've tried changing any setting I can think of, back and forth to see if something will stick, and nothing does. It also doesn't seem to be limited to extra large icons - it's thumbnails at any size.
Has anybody else dealt with this, and found a fix?