Backtest results from using RSI do not match with real charts

[thanitpra]

Hello,

I tested an MA strategy, which worked great and matched exactly 100% with manual backtesting from real charts.

However, when I tried an RSI strategy that is triggered upon oversold/overbought, I found that the backtester opened and closed at totally different points in RSI. For example, instead of opening a trade at RSI = 70, it was actually around 50-ish.

To make it more confusing, when I printed rsi.rsi, it still didn't match 100% with real charts but got much closer, e.g. 51 vs 54. On the other hand, RSI.plot gave a chart with way-off values but, of course, matched 100% with the backtester.

Can anyone please help explain what caused this discrepancy? I think RSI is a very well-known and old indicator. The math should be clear?

Thanks very much.