Mql5 OHLC, ATR

 
Hello, when i'm building EA sometime i get ATR/OHLC wrong values. After few attempt they start getting correct and they never becomes incorrect. I have no idea why exactly this happening. I'm guessing it happens when i change timeframe, or when EA is just attached to chart, somehow it needs to load some data to read correct values from OHLC table. 
 

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Providing more detail info. In code i have nothing different or complicated. 

int atrH = iATR(Symbol(),0,14);


double ATR()
{
        double v[];
        ArraySetAsSeries(v,true);
        CopyBuffer(atrH,0,0,2,v);
        return v[1];
}
This is what i'm using in EA. Imagine previous candle (index 1) ATR is 0.00391. But when i call ATR() function in EA sometime it gives me weird value for example 2.130214( i don't know any amount) and after few call of this function. It gives me correct ( 0.00391) value every time.
Just i need to know what causes EA to send incorrect value through ATR function.
Reason: