I have coal deposit with quality coal mineshafts discovered long ago. Today decided to build 2nd fast mine (the first is working ok - 45 secs). So i built it, upgraded to lvl 5 and start putting coal refills with intention to make it 100k+. At some point i clicked the mine and what i see - production time 1 min 30 sec - and i already put 81k coal in it!!! It's not discovered with the new geo for pumpkins - so it's and old bug?! It's pretty annoying!
