Well thats one of the many bugs that Sombra has since She launched.
I have a clip here:
With the Instand hack you probably mean this bug?:
Otherwise I never had a Hack that was instandly even after 200h on her.
Whats basically happening is that Hack breaks for no reason then the game reconnects it because it realizes the disconnect was wrong but restarts it at the beginning of hack (or thats what I think it does).
And I think I have another clip somewhere I will try to find it in the Meantime you can look at other bugs here: Even more Sombra Bugs in 1.26/1.27/1.28 [With Video's]