Hi Vitaliy

I suggest reporting this to the product support. It could be an issue with the Import.

I'm guessing that when you created the upload file to update the defects you did not enter any values in the detected_by column?  If this is the case, keep reading.  (Otherwise you may have found an issue to report.)  

From what I recall, basically if you want to update using the template, you need to complete all of the fields every time. Just including the one field you want to update does not work.  It's not so much an actual update but rather an overwrite.

The way to avoid this would be to ensure the template included the correct information on the upload. 

If I was doing this I would first do an export from Octane to Excel of the records I intended to update, including all the fields defined in the template (that you use in your configuration).  That way you would have the existing data already intact.  Then you would overwrite that file with the new data to insert and format the unique_id as mentioned. 

That way, when the file is uploaded it will not change the other fields, like you saw when your user performed the upload.  If there was no value provided, the system does populate this field with the active user by default

I don't use the Excel upload feature - I much prefer APIs for the control I have over any changes I wish to make.