Currently Mercy is not supposed to be able cancel GA after a slingshot or crouch jump (movement techs), but there’s a bug where if you frame perfect hit cancel GA and use movement techs the GA cancel works.
Seems easy but it’s almost frame perfect timing.
One good thing is that solves the broken synergy after a SJ (Super Jump) ressurect, where Mercy can’t GA away after a successful SJ ressurect wich feels awful.
In this clip Mercy is unable to GA away after the SJ ressurect in the first try but can in the second one with the GA cancel bug
In this one Mercy can’t GA away after a crouch SJ until she touches the floor plus some extra time, but on the second try I can use GA before touching the ground using the bug. It can be done with slingshots too but it’s even harder for some reason.
EDIT: As I’m testing the bug can also reset GA when using Valk (wich is bugged right now) there’s a delay, it’s not instant as it should be but at least feels better.