My only comment is that on a mac running Yosemite and Office for Mac I experience this also … outside WL. Between Office applications for example. Outlook to Word it happens a bit. That computer does not even have WL installed on it.
Never happens on my studio PC.
FWIW rant: I have had an irrational, strong preference for Macs for a period resembling forever. But the recent new OSX stuff really has me starting to think PC.