Summary of the bug : The shield stays active, even after dying in Arena mode.
When does this happen : While "racing"
On which track did it happen : Biodome
On which speed did that happen (if related to physics) : Any
How often does this happen : Always... at least if you replicate the steps below.
How to replicate the steps (if reproducible) : Play in Arena mode, pick up a shield, use it and wait to be destroyed by an opponent without losing your shield (by a mine or any front-facing attacks). The car is dead, but the shield stays active.
More details : Just noticed that it happens to opponents as well. If he had a shield and got killed, his shield stays active (cf. Screenshot 2).
Your specs : See here
Any screenshot, or link to a video showing the bug : Screenshot 1 / Screenshot 2