This is due to the precision and fees from Binance. We'll show it with an example.
Let say you wanna buy BNBBTC, with the minimum allowed by Zignaly, currently 0.0015BTC. Current BNBBTC price is 0.00357120, so you should get 0.42002688. But, you can't buy whatever amount you want. Binance requires you to buy it in lots. BNBBTC's lot size is 0.01 BNB. So, your 0.42002688, are rounded down to 0.42 BNB. You got 0.42BNB and you invested 0.001499904 BTC (buying price * acquired amount). Now you have to pay your fees. Fees are always from the acquired coin (unless you are not trading BNB and you have enable the option for paying your fees with BNB). Let say you have to pay 0.0750% on fees, meaning you have to pay 0.000315 BNB. You acquired 0.42 BNB, and you had to paid 0.000315 from those 0.42, leaving you with 0.419685 BNB for playing. Now the system places the take profit order (or you sell it manually, or by stop loss, trailing stop... whatever). Here we have the whole problem. We can't place a sell order of 0.419685, remember that the amount has to respect the lot size, which is 0.01 for BNBBTC. This means that the sell order has to be for only 0.41 BNB, leaving you 0.009685BNB without selling. Now see a 0.50% positive profit in the dashboard (that's gross profit, the percentage difference between the average buying price and the potential selling price (I said potential because a manual sell send a market order)) and we decide to sell. We bought at 0.00357120 and sell at 0.00358905, so we get 0.00147151 and still, we have to paid fees from that amount, which could be something close to 0.00000110 BTC (in BNB if you have the option selected). So your final return of investment is 0.00147041 BTC.
The return of investment (0.00147041 BTC) is around 1.97% lower than our investment (0.001499904).
Take in consideration, that because the lot size requirement, our bought amount was reduce from 0.42 to 0.41, around 2.3%. As lower is your position size, the worse. If your are trading with a position size of 0.5 BTC, then we would be buying 14 BNB, and after the fees, and lot size process we still would have 13.99, which is 0.07%.
Finaly, even when the position has sold less than it bought, you still have a small bag of BNB in your account (0.009685BNB), that you can use for paying your fees.
The trade is still profitable it is just the way it is being reported that makes it look like a loss. Imagine you bought 10 apples for $10 in total, you then held onto them for a few days and they were now worth $11. You want to sell them back again to the same company but the fee for selling them is 1/10 th of an apple. The company you are selling them to is not interested in buying 9/10ths of an apple so they buy the 9 from you for a total of $9.90 (11 /9). The way Zignaly would report it it would make it look you have lost in the deal. But you are still left with 9/10ths of an apple that you have not sold. However there is another part of the company that is happy to buy the 9/10th of an apple from you, its just not reported in the original deal.
You can get this error, in your DCA/ReBuy targets if the attempted buying amount is below the minimum allowed by the exchange.
It can happen that even when the re-buy percentage from the total position size is above the minimum allowed, due to the precision (check here how the precision works) the buying amount becomes less than it.
You will notice small balances of coins, below the minimum allowed amount for trading, in your Binance account.
The only way to get rid of them if to convert them to BNB, an option that we'll find in our Balance section, in our Binance account:
Once you click there, you will get a summary of all your assets with a small balance, and you will be able to confirm the conversion:
If the order was filled partially, yes we'll create a position with the filled amount and will sell at your desired point, unless the portion is smaller than the minimum permitted by the exchange to sell.
From your list of positions, you will see sometimes a number of DCA/ReBuy targets in red, meaning that they failed.
To know the reason, you just have to go to the position and locate the DCA/ReBuy target box:
If you pass you mouse over the red icon, it will tell you the reason of the fail:
The system doesn't retry again when a DCA/ReBuy target fails.
When you don't pay the fees with BNB (or your are trading WHATEVER/BNB), the commission will be subtracted from the acquired coin. For example, for a position QTUM/BTC the buy commission will be deducted from the QTUM obtained amount and the sell commission from the new BTC acquired amount. Due to the Binance precision requirement, it may happen that your buy amount - the commission has to to be rounded down. So, you buy 300 QTUM, pay a commission of 0.3. You would have 299.7 for selling. Because the precision is 0 decimals, it'd only leave you to sell 299 QTUM, leaving you with a 0.7 bag of QTUM.
If your position size is small, this could reduce your net profit considerably, even make them negative.
Even when the position has ended with a negative net profit, take in consideration that you still would have a small balance of that asset that is not computed. Remember that you can convert your small balance to BNB.