Hello Graham, Did you find any workaround or the cause of this error? I get the same error for a particular stock (WMT) when trying to buy with a limit order on a live account even with round amount (138.00). When requesting ContractDetails I verify that the minTick is 0.01 so, that is not the problem. The same transaction goes well on the paper account but it is not accepted on the live account. Using TWS Build 981.2r, Feb 10 2021. Trying hard to find someone with a solution but no success so far. Just one guy reported that sending a request with transmit = False, waiting some time and send the same with transmit = True solved the problem.
Very?frustrating that I missed a trade yesterday due to this unpredictable transaction rejection.
