Prior to v2.11 app, when scrolling through the events list to delete events, the select all and cancel stayed on the screen so once you get back to the very first event thumbnail, you can hit select all and delete.
Now with the v2.11 app, the select all/cancel button disappears when you start scrolling through the events for deletion. You have to scroll all the way to the bottom to the first event. Then, you have to scroll all the way back to the top to click on select all to delete them.
This could be an Android bug only.