RSI is similar to MA - each point is a result from X candle values. Candles are built from few points as well - open, close, high, low, and in addition to that there are other points, like the medium price. So you can decide to built RSI based on one of these points. This has nothing to do with the count of ticks per minute.
In your case, you compare the value of RSI for the current candle, but because you have "Once per bar", you do that when the candle is brand new (a single point actually). The RSI value of that moment is something that will not stay the same for long, and you will never see it again, because it is temporary 🙂