First time just open the epic battle from clan page. From that point you can open it from home page. Using cache cleaners or task killers its not a solution. Task killers fix an issue on short term but its causing lag and battery drain later (the background processes killed by task killers will start again using more resources and battery).
It happens in all android. It's a bug. Close ap. Restarting will fix the issue. If it annoys you that much email Support@athinkingape.com telling them as much info.
Whenever I hit an eb and that eb finishes I have to restart my game. That has happened ever since I got my new android phone. Sooooo…