Rendering of stereo effects with UI duplicates the statments

[anton-k]

If we use uiPongy or uiRoom we can clearly see that the effects are duplicated.
If we have the stereo effect like this:

(a1, a2) = fx args

The rendering algorithm is going to use it twice. And it takes the left case from the first run and the second case from the second run:

(a1, a2) = fx args
... do something ..
(a3, a4) = fx args
... do something ..
process a1, a4

And a2 and a3 are dead ends. That's a bug,