Fix json serialization + preloaded candle

src/Managing.Application/Bots/TradingBot.cs

@@ -217,6 +217,12 @@ public class TradingBot : Bot, ITradingBot
         if (OptimizedCandles.Any())
             return;
 
+        var haveSignal = Signals.Any();
+        if (haveSignal)
+        {
+            PreloadSince = Signals.First().Date;
+        }
+
         var candles =
             await ExchangeService.GetCandlesInflux(Account.Exchange, Config.Ticker, PreloadSince, Config.Timeframe);
 
@@ -226,7 +232,11 @@ public class TradingBot : Bot, ITradingBot
             {
                 OptimizedCandles.Enqueue(candle);
                 Candles.Add(candle);
-                await UpdateSignals(OptimizedCandles);
+
+                if (!haveSignal)
+                {
+                    await UpdateSignals(OptimizedCandles);
+                }
             }
         }