Different data feeds produce different charts, especially when using tick based intervals vs time based intervals. Market data vendors each employ various methods for tick filtering, throttling and time stamping. As a result, no data stream is 100% identical and thus can cause subtle differences in charts. Since NinjaTrader supports many of the leading brokerage and data feed technologies, it is highly likely that two traders using NinjaTrader on different data feeds will have minor differences when plotting the same market and time interval, or when comparing to an external source such as TradingView.
More information can be found below in NinjaTrader 8 Help Guide article regarding this topic:
https://ninjatrader.com/support/helpGuides/nt8/?how_bars_are_built.htm