When Rek'Sai lands from using her ultimate, sometimes she will have a small pause before she continues attacking. If you activate Q (queen's wrath) after landing it can result in an even longer delay and a visual bug as well.
Rek'Sai will occasionally get stuck on walls when trying to tunnel through terrain.
If a ward is placed on top of a tunnel entrance, you can't click on it. This includes ally wards....
