Teferi, Time Raveler (Vanguard) +1 ability works only on spell at 1st slot of the hand [Investig..]

Some time ago I had problems with that ability (it was causing random freezes, upon using it - especially with cards with adventure on their spell half), however that problem was resolved. Now I can only use this ability, when a spell in the first slot during battle. Moreover, it doesn't work now at all for adventure spells.
It should for for any spell in hand, since the ability states: "The first spell in your hand (...)". 
PS: Used Vanguard in the title, if normal Planeswalker with that name would appear in game at some point.