Yes, this is a known quirk (see
this thread) of v1.25.0 (and common to all SG v1.4/1.5 based viewers). It is apparently an issue in the pre-built qtwebkit library as provided by LL. It is harmless and will go away when I will find time to delve into the media code so to update to the latest qtwebkit builds used in the latest v2 viewers.