Getting the same values as Tradingview.
Make sure the time zone is correct on tradingview to compare. 
When the exchange  data fails Tradingview cut out the data that is missing but gekko just freezes and all the numbers go to the same for close, high and low candle. Then causes the K and D numbers to NaN, stopped this with - if (candle.high !== candle.low).
Added Smooth K, set to 1 to disable
Takes 5-6 candles for K % D calculations to catch up initially ?? not sure how to correct this

Test with:

var method = {};

method.init = function() {

    this.name = "Tradingview-tester";

    this.addIndicator('ind', 'STOCH', {KPeriods: 5, DPeriods: 3, smoothKPeriods :2});

};

method.check = function() {};
method.update= function(candle) {

    console.log("Time: " + candle.start.format())
    console.log("High : " + candle.high);
    console.log("Low : " + candle.low);
    console.log("Close : " + candle.close);
    console.log("LL : " + this.indicators.ind.getLowest());
    console.log("HH : " + this.indicators.ind.getHighest());
    console.log("%K: " + this.indicators.ind.K);
    console.log("%D: " + this.indicators.ind.D);
    console.log();
};
method.log = function() {};

module.exports = method;