Through the Ages error

I find it funny that sometimes after playing a game so many times and thinking that I'm already an expert, I suddenly discover some rule error which I have been playing with from the beginning. Usually they are not too bad. Else it probably won't be so funny, and the game probably won't work well enough to warrant many plays. I just discovered another error I made with Through the Ages. When you have discovered a more efficient form of farming or mining, you are not allowed to "upgrade" two or more blue tokens from older farm/mine technology cards to fewer tokens on the newly played farm/mine technology card. I have always thought that you can do this any time, i.e. you get a good efficiency boost the moment you discover the new technology.

However you can make change, i.e. if you have one blue token representing 2 stone, and you need to pay 1 stone, you can move that blue token down to the Level A mine, so that it now represents 1 stone.

If I have 3 blue tokens on my lowest level farm (each representing 1 food), I should not be allowed to convert them into 1 blue token in my higher level farm (where 1 blue token represents 3 food), thus returning 2 blue tokens to my bank.

I still have no news about the fix pack. My Through the Ages is the 2nd edition (or 1st edition published by FRED), which has the score track error and some non-critical errors on some cards. It is also short of some tokens, but since I have never played with 4 players, I have had no issue. But it would still be nice to receive the fix pack some day.