Corrections to EA

I made a very simple EA but I get error "OrderSend error 130" in all backtests done in MetaTrader 4. I don't understand why the EA opens succesfully some trades (it is a long only EA) but it returns this error for some other trades. I think a checked correctly this error is not due to any of the next reasons:

• stop loss and take profit are set as prices, and they are well established for a buy stop order, which is the way I'm trying to open each position.
• it is said on some webs that ECN brokers (I am doing the backtest with Admiral Markets UK, which is a ECN borker) don't allow to use non-zero TP and SL when using OrderSend command. Instead, 0 must be used for these values and then replaced with OrderModify. I don't think this is the problem because, if this were the problem, why some trades are succesfully placed doing exactly the same?
• stop levels are not enough close to open prices for the broker to give an error. Typically SL is placed about 50 pips (in 4 digit broker, 500 in 5 digit broker). I am using a 5 digit broker, since the command Digits returns a value of 5.
• ope price, SL and TP are normalized double to Digits, so I don't expect to have any error for this reason.