[Influx DB Cloud TSM] Different results for the same Flux query executed on same dataset

I have a relatively simple Flux query, that I’m running a static set of data in an InfluxDB Cloud TSM:
from(bucket: “ipet004”)
|> range(start: 2023-12-31T22:00:00Z, stop: 2024-02-26T22:00:00Z)
|>sort(columns: [“_time”])
|> filter(fn: (r) => r._measurement == “testEq006189” and (r._field == “speed” or r._field == “eventCounter”))
|> aggregateWindow(every: 1s,fn: mean,createEmpty:false)
|> pivot(rowKey:[“_time”], columnKey: [“_field”], valueColumn: “_value”)

Whenever I’m executing this query via SoapUI (REST client) I get 80-90% of the times the same result, but in the other cases I get a different result set.
By different I mean I see a row appearing in the dataset (at index 2, in case it’s needed to know) that does not increase the result set row #, but it effectively shifts all the other rows.
My dataset is static 100% of the time, so I’m puzzled why would this happen?

A sample result set containing first two result rows (rest are very similar to row 2):