the ghost shells seem to be much more common as of late. For the lucky ones who haven't encountered this: a "ghost shell" is a bug where the shell simply passes through the target without doing any damage. It is usually associated with packet loss and desynchronization but in some cases (a few patches ago) there's a bug in the game that makes them appear much more than usual.
Here's another example of a ghost shell:
And here's the replay for this battle.
Have you encountered the ghost shells yourselves? Let Wargaming know!