Some minor inconsistencies with tag exporting

when exporting tags, there are some issues.

“length” from the “extended fields” list outputs blank data.

the duplicate “length” from the “information fields” list outputs correctly.

the “_length” field outputs time incorrectly. for example in the app 30 minutes shows as “30:00” but exports as “30:00:00”

“tag” field displays in the app as “ID3v1 (ID3v1)” but exports as “ID3v1 ID3v1” without parentheses

Please note that LENGTH is a text field that has very little to do with the actual length of track. You can write more or less any value into that field without any influence on the length - even a text like "this is the length".
A output can only be generated if there is any contents for a field. A field whithout contents does not exist.
If you refer to the file property length as written by the encoder, then use always _LENGTH.

I think that this should also be _TAG.
Check where you see

If that is the column in the file list, check the column definition which may have the label "Tag" but probably has set as
Value: %_tag_read%[ (%_tag%)]
Which shows you which tag is read and which tag versions are present in a file. _TAG then shows you all tag versions, e.g. ID3V2.3, ID3V1, APE.

Is this how your csv-capable app shows it? Or is this really from the plain text in the csv-file?

yes. see attached screenshot. 39 hours 11 minutes 00 seconds is actually 39 minutes 11 seconds. seconds shown in column D for additional confirmation.

That looks to me like a problem of the importing program and not an MP3tag problem.
See e.g. this thread that deals with a similar problem:

so sorry I should have looked at the raw csv (text) file.

2351;39:11;