No StopLoss on market order but I still get Error #130 Invalid Stops?

Stop/limit orders might lead to the mentioned error even if they have SL=TP=0. If you are absolutely sure that your EA places only market orders then my comment doesn't apply.

Thanks bstone, do you know why it sometimes occur with STOP or LIMIT orders? I'm wondering if it's a platform issue, or if it's the broker. The weird thing is that I can always place trades on my master platform, it's when the order is placed on my slave platforms by the EA that the error occurs, and they are placed immediately and all using the same broker. I would think that if an order can be placed on one account with i.e. FXDD then it should be possible to place the same order on other accounts with the same broker, especially with STOP or LIMIT orders.

That will depend on the lag between your master and slave systems. If your stop/limit orders are very close to the market and the price moves 1-2 points away while the master and slaves are synchronized, you'll observe this problem often.

A possible solution is to make your slaves intelligent enough to adjust stops/limits based on the current price and broker's stop levels. That is, if the slave sees it can't place stop/limit exactly at the same level as the master, let it place it at the minimum possible distance from the reference level.