Regarding the 15 minute charts:
There has indeed been a problem with them and it will be fixed 'shortly'. Because the 15 minute charts are not a 'major' timeframe in Delta Trading the 15 minute bars are constructed from the 5 minute bars (once they have closed) so if you're actually PHYSICALLY sitting watching a 15 minute chart it will APPEAR as though the 15 minute chart is updating 5 minutes 'late' but this is not ACTUALLY the case insofar as price / OHLC is concerned. Put it this way: if you opened and closed a 15 minute chart every fifteen minutes you would see that the OHLC, as taken from the 5 minute charts for a 15 minute period, will be correct (notwithstanding the fact that, as noted, there has indeed been a problem with the 15 minute charts which is being corrected as we 'speak').