Good video, nice to see that you can have pitstop failures too (he refers to a jammed wheel gun, I guess the engineer gives you that info?).
Yes, the pit engineer tells you when something goes wrong at the pit stop
When he pits there are no mechanics present other than the "lollipop man"; is that just a replay thing or is there no animated pit crew in-game yet?
They worked hard on them in the last weeks (just read up the build notes) but it looks like they won't be ingame at release. No replay bug.