Reserves are balances held at the fed. Excess reserves are balances in excess of that required by the fed. The overnight rate falls. I don't call that a crisis. It could be a policy decision.
Banks can always pay interest.
The point is they won't if they can't earn it on the other side. But no matter. Misses the logic completely. Moore's, Wray's, and Goodhart's say definsive all the time. That is due to rounding, caution, and calculation error.