Wow this has really messed me up for 2 days and cost me tons in Gems, Coins and Resources trying to figure out why my coal was so low. Then this afternoon I found this glitch which I am pretty upset about and hope you all at BlueByte will make right with me and also fix with your maintenance.

As you can see these two mines are upgrading to level 3 however they producing at level 2 and also the cost to upgrade to a level 4 is only 500 which is the cost to upgrade usually to a level 3. Obviously when my upgrade was done it never took however its level moved up to 3 even though it is fully acting as a level 2.

I also took a screen shot of a properly upgraded mine however felt there was no need to post it since you obviously know what one looks like, however its available if you need it.

UPDATED:
REMOVED IMAGES FOR PRIVACY REASONS!