error or incompatible results in sort function

[aisiklar]

Hello,
I have a question / problem related with sorting. Which is weird.

I will do my best to explain the issue.

I have a data written to influx. For simlicity, let's say that my data is:
username: field
name: field
surname: field
time
There are also tags of course but not relevant with my problem.

My query is as below:
from(bucket: "x-bucket") |> range(start:1702281528, stop:1703224380 )
|> filter(fn: (r) => r._measurement == "x" )
|> pivot(rowKey: ["_time"], columnKey: ["_field"], valueColumn: "_value")
|> group()
|> sort(columns: ["_time"], desc:true) // This is for secondary sorting
|> sort(columns: ["name"], desc:true) // this is for primary sorting
|> limit(n:100, offset: 0)
|> yield(name: "x")

I first sort data according to either "name" or "username" or "surname" THEN sort according to time within these sorted data.

I have a "not_found" value for username, name and surname, when a case appears in the app, written to db.

So typically, when I sort acc.to username (primary sort is username) then the result is as follow

time name surname username
18.12. tarik arabaci tarabaci
17.12 tarik arabaci tarabaci
16.12 not_found not_found not_found
15.12 not_found not_found not_found
14.12 murat dursun mdursun
13.12 leyla arici larici

which is correct, or at least what I expected...

BUT, if I sort according to name or surname as a primary sorting item THEN the result is as follows.

time name surname usernam
16.12 not_found not_found not_found
15.12 not_found not_found not_found
18.12. tarik arabaci tarabaci
17.12 tarik arabaci tarabaci
14.12 murat dursun mdursun
13.12 leyla arici larici

See that, not_found is displayed at the top, which is wrong... But other data is sorted as it should be.

Therefore, if primary is username, all is ok but if it is name or surname, there is an error...

I think, my query might be somehow wrong, or at least not giving the expected result at all conditions... Because, on the influx Data Explorer, if I click the header of the table to sort it (not with query), the sorting is done correctly...

Therefore, does anyone have an idea what I am doing wrong?

Thanks,
alptekin

P.S.
I am using 2 lines for sorting and not as |>sort(columns:["primarySortItem", "secondarySortItem"], desc: true) because, in future I might sort primary and secondary items different in terms of desc key. like, primary is sorted with desc: true and secondary is sorted with desc: false...