Hi Chief,
It occasionally happens that the countdown timer for an upgrade stops. Don't worry! Your upgrade is still progressing, but you may need to restart the game to fix this.
Also, when you are offline, other players who are browsing for villages to attack can visit your village, and these visits might cause a small delay to your upgrades. This delay is minimal, but if you get many visits it may become noticeable.
Our team is aware of this issue and is looking into it. Our sincere apologies for any time lost.
Clash on!