Hello Petko,

The option "Use previous bar value" states when an indicator uses values from the previous bar for calculating the current bar signal.

For example, if an entry rule indicator uses "Bar Close" base price, it obviously cannot produce a correct signal until the end of the bar, however, if the strategy opens a position at, let's say Moving Average, it may happen at the middle of a bar. FSB will use the previous values of the entry rule indicator for filtering the entry at MA. The opposite, would be looking in the future and would produce highly overestimated backtest results.

The above example is relatively simple, but there are some very complex cases and it is very difficult to decide whether to check on or of the option.

We fixed that issue by adding a complex algorithm that makes these decisions instead of the users and checks on and off the option automatically.  We found out this behavior more safe for the traders.

Here is an article for the Use previous bar value option.

Haiken Ashi bars uses the full bar range. It means that the bar must be completed in order to have a reliable signal.
The program correctly uses the previous bar value. In the other case it may give you a false signal.

Lets see an example.

Lets to be noontime. If the current bar is bullish and H.A. allow long entry, your strategy may open a long position. Let's at the end of the day some "bad" news force the market down and it finally close below the opening. Your long position would be at a loss. Let's several days after that trade we import the history in FSB Pro and perform a backtest. In the backtest we will see a bearish bar for that day and no long position. This is discrepancy between the backtest and the real signals our experts produce. Such strategy is so dangerous that you may lose your money and will not understand how. (It really happened to me 15 years ago, and took me 4 months to understand that the reason was indicators that repaint the signals).

...

This was not the problem with the LTF indicators. They work just fine if you know what to watch. An LTF indicator may show discrepancy in an Expert Advisor if it uses Exponential smoothing, the main time frame indicators use Simple smoothing, and relatively short periods. In such case, the EA cannot determine how much bars exactly are needed for the LTF indicator sin order to produce stable signals (as you know the Exponential smoothing depends on the history length).

It is safe to use LTF indicators with Simple smoothing.
When you want to use LTF with Exponential smoothing, you have to watch how many bars the expert loads. If it loads a small number at startup (let's say 200 - 300) you may manually set the count in the expert code.

All these issues are perfectly detectable when you compare the indicator values in MT and in FSB chart.