There is currently a bug within the Buy Resources area.
It concerns the FULL & AVERAGE button.
If you hit the full and average button it uses all your GOLD to buy resources. However it does not take into account the upper limit of your resources..
Basically if you have;
10,000 gold, it will use it all
20,000 gold it will use it all
50,000 gold it will use it all
100,000 gold it will use it all
It uses all yours GOLD, and your resource allowance for the day.. regardless of how much you can store in your city..ie (you will just have red resources, FULL)
B