The monthly task does not work

Hi Community!
Need help to figure out why my monthly task doesn’t run only the first day in every month. The result is the task runs twice 1st and 18th every month, super strange!

Option task = {name: “Energy_month”, every: 1mo}

from(bucket: “SensorData_2”)
|> range(start: -1mo)
|> filter(fn: (r) => r[“_measurement”] == “Energy_day”)
|> filter(fn: (r) => r[“_field”] == “Wh”)
|> aggregateWindow(every: 1mo, fn: sum, createEmpty: false)
|> set(key: “_measurement”, value: “Energy_month”)
|> timeShift(duration: -1h)
|> to(bucket: “SensorData_3”)

@Anaisdg - please can you guide/help me on my question above, thanks