When modulating the envelope times you have to modulate them by a negative amount to increase the time.
Too counter intuitive for it not to be a bug.
I can confirm that this is how Pro 3 envelope modulation works, though. Positive modulation makes the times faster, negative modulation makes the times slower. It seems pretty intuitive to me.
It's the opposite of the pots if you think of "clockwise" as "positive," so I can
sort of see where you're coming from. But I don't think it's a bug, or at least one unique to Take 5.