Thank you for your replies, Steeltorin, however I have this to add. The excess amount of food I have is over 3M, while the amount of lumber and iron is just over 1M. Silver is over 4M, while stone is about 800k.
All my buildings are either at Palace level (L14) or just 1 level behind, so your suggestion I should upgrade my buildings isn't relevant to the issue.
I complete about 1 building upgrade a day, and the past 3 days they have been farm upgrades from L13 to L14. These upgrades use just a few K of lumber, iron and stone. Even without production boosts I am overproducing far in excess of 10k/hr in each of those resources. Therefore I should expect to see the amount of each of those resources increase between logging off one day, and logging back on the next after 12+ hours have elapsed. However, there is no increase in any of the resources. In fact, particularly in stone it seems the total amount I have in stock appears to be dropping, as the lower amount I have allows me to more accurately gauge the day to day totals.
It is not an issue of how much of each resource my town can hold, as the disparity between the amount of food and silver I have compared to the other resources demonstrates. I have gathered some resources via farming tiles rather than town production, particularly silver, but even if the capacity is down to the number of buildings for each resource I have, then I am way over what I should be able to hold in food and silver - therefore the capacity is not an issue.
At various other times in the past I have had a lot more of each resource in stock, either as a result of pillaging towns, farming tiles or from convoys others have sent. So, if capacity is the issue, why have I been able to hold more stock than I currently have?
You say "Resources have produced constantly, but if capacity became full, producing will stop." but that is put to the lie by the fact you can hold much more stock of resources than "capacity" seems to indicate. There is no apparent limit to the amount of each resource your town can hold.
If Plarium have implemented a limit on the total amount of resource you can produce in town, but set no limit on the total amount of resource your town can hold, then that is just a ridiculous ploy to prompt people to have to pillage other's towns or farm resource tiles to make up the difference. The game allows a person to build a town that is balanced in supplying resources for the amount of activity the player undertakes (upgrading, troop building, etc) - why nerf that?