There was a change with the way Sinclair ult works since the new heroes have come out. They broke it (presumably to make it work with wolf form) and have been just patching it together since. Lightning scroll no longer works with Sinclair on any non-channeled ultimate.
Lightning scroll only works if you are still the pink version of that hero at the time the ultimate damage is applied. Good examples of this are Bebop, Seven, Mo, Viscous, Dynamo.
An easy way to reproduce this bug is to steal Ivy ult. If you throw the bomb and continue flying, Lightning Scroll will work. If you cancel the ult to throw the bomb, Lightning Scroll will not proc.
in a sandbox, if you re-steal the ultimate, Lightning Scroll works while you are holding that ultimate. Presumably the same could be said of refresher in a real match.