'Shield Drive' at the last stack if you use defend it doesn't stack with the last 'Defending' stack and removes the 'Defending' stack buff instead.

[Papum]

When using Shield Drive and it is at it's last stack and than using defend it doesn't stack with the already last existing Defending stack and removes it instead, yet when it is not at it's last stack it stack up several times (using it with Brint's Arena armor set).

Build: 0.8.13