I see you’re using Ninja’s builtin CumulativeDelta indicator in your code which tells me you must have a 1-tick secondary data series defined in your script as required. OnBarUpdate() will run once for each DataSeries in your script. The 1-tick data series is a bunch of bars that include a single tick therefore each time your 1-tick series is processed, the IsFirstTickOfBar is set because it is the first tick of the 1-tick series.
To fix this, you need to check BarsInProgress so that you’re only looking at the primary series. My suggestion is to use a test like (BarsInProgress == 0) around your Print statements or it might make sense to place that check at a higher level. I don’t know the rest of your code and don’t know what you’re trying to do so I can’t tell where it’s appropriate to have this check, but unless you have this check somewhere, you will see exactly what you have described which is the Prints will happen on every incoming tick.
Hope this helps.