Rek 'Sai Tunnel of Bugs.
Bug one: not sure what exactly causes it but it seems to be paired with any activated item or summoner spell that if I go to tunnel a good 1-2 second after using said spell or wepon, the tunnel will be created, but Rek 'Sai will stay in place. This leads to some really unfortunate deaths when running from a chase or loss in keeping your placement in a team fight.
Bug two: Might not actually be a bug but something I don't much care for is that placing wards over top of tunnel holes complete negates the use of them. whether it be re-using them or trying to ult to them. It makes it impossible to use them and certain users have taken note of this and have taken it upon themselves to troll Rek 'Sai players in game with this.
These might seem a bit minor, but they are enough to make things a bit more of a tideous issue.