I shall post this in the bug report forums aswell, BUT... here goes.
When you are capping a point, if a sunfire cape says 'NOPE, stop capping!' it will stop you from capping, but the visual on the mouse of when you CAN cap again will not go on cooldown, it will just stay green.
Although, when this did happen for me, Garen (the person with sunfire cape) was in the fog of war, at the top point. (so he was behind the triangular terrain, with sunfire cape, it proc'd on me.. stopped, etc.
1: Have two champions
2. One buys sunfire cape, one does not.
3. Proceed to top point, where the one with sunfire cape hides in the fog of war, but just able to proc sunfire on the person on the point.
4. Have the Person without sunfire cape attempt to cap the point.
5. (repeat 4, although have the player with the sunfire cape move in and our of range to see where the bug actually happens (like at the start, end, or middle of a capture.) Also test For neutralising points and for capturing points.)
6. Praise thyself =D