When moving gold from the City to the Trader and you create an outgoing flow of Gold to purchase items, the gold amount in your Trade-hub will diminish, but the transfer amount requested from the city to the trade-hub does not take the diminished amount in account and will keep shipping gold to the detestation pool, until the amount reaches the before set gold limit.
The transfer amount should be decided on the current requested movement, not on the destination current pool value.
When the total city gold amount lowers under the target movement, it will even keep the movement active, while the movement will never be able to complete.