This happens because, for different timeframes, there's a different periodicity. Over longer time frames, a 50 period moving average may be a 50 week or even month moving average rather than a more typical 50 day moving average. Above the moving averages, there's a flag to indicate weekly, monthly or daily charts and the SMA switches between each. Currently it switches as you change timeframes.
This is a limitation in our charts package that handles the core algorithm in this way - we are intending on sorting this out in a future development sprint.