Since I pickd DragonScale specielization for leatherworking, I can't open AdvancedTradeSkillWindow2 anymore by clicking on the leatherworking nor dragfonscale leatherworking icon. It can close it correctly though.
I can open it through any other profession and switching tab (a bit buggy but it works).
It works fine with the original AdvancedTradeSkillWindow so I take it's linked to something that has changed since.