Regarding the fonts themselves, I can see that the Ubuntu-M.ttf's "Family Name" says "Ubuntu Light". Fontname and name for humans are Ubuntu-Medium & Ubuntu Medium.
More inconsistencies include that Ubuntu Light has all Fontname / Family name / Name for Humans as Ubuntu-Light or Ubuntu Light, where as the Ubuntu Bold has family name only "Ubuntu".
As the last possibile thing to check is Styles (SubFamily) setting in TTF Names, which is "Bold" for both Ubuntu Medium and Ubuntu Bold, and "Regular" for Ubuntu Light.
Regarding the fonts themselves, I can see that the Ubuntu-M.ttf's "Family Name" says "Ubuntu Light". Fontname and name for humans are Ubuntu-Medium & Ubuntu Medium.
More inconsistencies include that Ubuntu Light has all Fontname / Family name / Name for Humans as Ubuntu-Light or Ubuntu Light, where as the Ubuntu Bold has family name only "Ubuntu".
As the last possibile thing to check is Styles (SubFamily) setting in TTF Names, which is "Bold" for both Ubuntu Medium and Ubuntu Bold, and "Regular" for Ubuntu Light.