Created attachment 123889 [details]
Screenshot of LO gtk3 with broken scrollbars in Ubuntu 15.10
When LO is launched with SAL_USE_VCLPLUGIN=gtk3, the scrollbars are broken: the slider within the gtk3-style scrollbars fills the area of the scrollbar with its color just like a paint brush.
Upgrade to 16.04 and you will find that the scrollbars now draw properly. It was a bug in ubuntu-themes.