Ever since the bullet reporters test build I have often encountered this bug where the LOST THE FLAG message is delayed by many seconds. In 5.12 this has not been occuring less, perhaps even more. It seems to happen more often with people with less stable connections. Gameplay-wise the biggest issue isn't even the moment when the message is not appearing, since you can at least still see the kill message, but when it is appearing. Since its so much later it could coincide with another flag loss from another player, creating a lot of chaos and confusion (on your screen).

An example: