Thanks for playing and for the feedback :) This is actually not a bug, it is just a feature that is not explained ^^ They stop trading for acorn for wood or water for stone when you don't have that many acorns/water to spare. Basically a part of your acorns and water is always reserved for the squirrels needs, since otherwise it happend quite often that you assigned too many squirrels to a trade post and ran out of water/acorn. This mechanic should have definetly been explained in the UI, but we ran out of time ^^