Why Does the MQL5 strategy tester give different results when the same hard-coded strategy is used on a different time frame?

[Jimmy9618]

If I hardcode the time period, for all the ema handles as Period_H6 for a simple ema crossover strategy, and run the tester with H6 selected, as expected it provides a profitable result. However when I change the tester time setting to H4, it gives a different and much worse result. There is no Period_current in the advisor, nor any other code that would suggest any other time than H6. Does anyone know why this would be?