Talon's stealth not working

Need some help with a bug I keep getting in matches where casting shadow assault is either not giving me stealth or breaking the stealth early. Can someone help me better understand what's causing this bug, because it's costing me matches, which is kind of annoying. Here's 3 different examples of what I'm talking about:

Clip 1 : https://imgur.com/OypDdMt

Clip 2: https://imgur.com/4KVXR9y

Clip 3: https://imgur.com/awMH1DV

Any help from another player or rioter would be greatly appreciated. :)