After using Soraka's ultimate, the actual cool down displayed was much longer than the cool down shown on the ability description.
Some more details:
-Only happened once that I noticed. The next time I used the ultimate it used the correct cool down.
-Was not because of purchasing items or getting ultimate hunter stacks after the ability was put on cool down (the picture is taken immediately after using the ultimate)
-Had ultimate hunter rune
-Couldn't recreate the bug, but have a replay saved of it