Is the animation group/animation feature with fontstring objects broken or something?

[Duugu]

I'm currently working on an action bar mod and I'm creating action buttons via Blizzards ActionBarButtonTemplate template. Works as expected. I'm not doing any modification to ActionBarButtonTemplate. Is't the pure Blizzard template.

If I create an animation group/animation (rotation) on a frame that was created via ActionBarButtonTemplate then the frame itself is rotated as expected. But the fontstring object, that is part of the ActionBarButtonTemplate template, is not being rotated as expected.

My code is like:

local tFrame = CreateFrame("CheckButton", nil, UIparent, "ActionBarButtonTemplate")
local ag = tFrame:CreateAnimationGroup()
local a1 = ag:CreateAnimation("Rotation")
a1:SetDegrees(90)
a1:SetDuration(10)
ag:Play()

The result is like this:


Compare the the Blizzard action bar buttons on the bottom and the rotated ones in my bar. The frame, the texture ... everything is ok in my bar. Except the fontstring showing the stack size. It is ... somewhere and somehow weird rotated.

Has someone an idea why this could happen or if animation groups with fontstrings are working at all?