An enemy Sombra must always be paid attention to--take it from these guys. In a clip from,
u/pastell_soelli, a Sombra pulls off an incredible back cap. While the blue team pushes up to the choke point, using the whistle of Bastion's ultimate as a rallying cry, the red team's Sombra is able to slip around a side lane and find her way to the payload. She is careful to not be spotted, even hesitating for a moment behind a wall to ensure that the respawning Orisa doesn't spot her. Once she made it to the payload, she is again very careful to stand behind the payload and avoid giving her enemies line of sight.
She staggers her movements to bring the payload home and complete the good ol' back cap.
It's difficult to pay attention to the payload when the hectic team fights break out. Many payload maps operate as a series of choke points that the attacking team must breakthrough in order to keep the game going. During these team fights, its crucial that players keep an eye on the HUD and make sure that the payload isn't moving. The crucial mistake in this video is that the team decided to set up a choke so far from the payload. They should have set up a choke point and had one player walk the payload back to ensure that they could not be back capped. Kudos to the Sombra for a heads up play that ended up being the difference in the game!