I’ve observed this bug a large number of times, but here’s the first time I’ve got a video of it. Someone is downed, you revive them, the bar goes all the way to 100%, the animation indicates that it’s complete – but it doesn’t actually get them up. They fall back down.
This can be and often is a run-ending bug. This happened to me today in the ending hallway of Refinery Delta (damnation/hi intensity shock troop gauntlet difficulty), when I was the last one standing. I used my Until Death proc to “revive” a downed teammate, which “succeeded” visually – except it didn’t actually get them up, and then we wiped. This was at the very end of an extremely wild 50 minute mission, which is just the icing on the cake.
Edit to add: this is something my friends and I have observed many times in our runs and often comment upon (“what! I got you up!! what the heck it did the thing again!”). I’ve actually developed a habit of holding down E a little extra time because that maybe seems to help, although in this case it did not. It seems more likely to happen in situations where there’s a lot of stuff happening on the screen. I’m guessing the underlying cause is the server getting overloaded and not registering things (e.g. the well-known hitreg bug).