There are many Hack breaking bugs (Here are a few Vid’s:)
Hack not finishing - YouTube.
Hack takes a little longer - YouTube
Hack may takes a little longer but it doesnt work anyway - YouTube
Sombras Long hack - YouTube
As you probably noticed some of these did not completely broke they where just longer which happens when It breaks and the re-attaches itself faster then it should.
There is not much do to about it other then hoping it will get fixed someday. I will leave my Sombra bug post here: Even more Sombra Bugs in 1.26/1.27/1.28 [With Video's] I hope it will help you somehow.