Why did my Chattermill NPS or CSAT numbers change after a data upload?

What causes it?

1. A change in the date format of your data can store dates wrongly, so responses can land on the wrong days and move a day's score.

   In the Chattermill help: If the date format was to change, the date field may be stored incorrectly, or the response may not be uploaded at all Data guidelines, read 2026-11-12.

2. Scores need to be sent as numbers, so scores sent another way can be read wrongly or left out.

   In the Chattermill help: Scores must be in a numeric format Data guidelines, read 2026-11-12.

3. Each response needs an ID that has not been used before, in any earlier file, so reused IDs can make responses clash.

   In the Chattermill help: This Response ID must be unique across the entire history of the dataset including previous files Data guidelines, read 2026-11-12.

4. A file sent with the wrong text encoding can garble characters in comments.

   In the Chattermill help: If a CSV is sent with incorrect encoding, some of the characters may not be displayed correctly. Data guidelines, read 2026-11-12.

How do I check it myself?

1. Check that every date in a file uses the same format.

   In the Chattermill help: All dates within a CSV must use the same date format. Data guidelines, read 2026-11-12.

2. Check your files for repeated response IDs before they are sent.

   In the Chattermill help: Please check for any duplicates of this Response ID within your files before sending to us Data guidelines, read 2026-11-12.

How does Chattermill work with Feder?

• Connect Chattermill to Feder and it joins your Experience apps.
• When you connect Chattermill, Feder checks the connection straight away and shows Connected only when that check passes. If a reading cannot be taken later, Feder shows it as not read, never as zero.

Some numbers are too quiet to judge daily, such as a form filled in a few times a week. Until there is enough of your own history to judge a change, Feder says it is still learning and scores nothing, rather than guessing.

See whether you can trust the numbers in Chattermill, one of your Experience apps. Feder only reads. It never changes anything in Chattermill.

What else goes wrong with these numbers?

• Why did the number of responses in Chattermill drop?Chattermill
• Why did my sentiment score drop in Chattermill?Chattermill
• Why did Google Analytics stop collecting data?Google Analytics
• Why aren't my key events showing in Google Analytics?Google Analytics
• Why does Google Analytics show (not set)?Google Analytics

See every question.

Where do these answers come from?

Every cause and check on this page comes from the Chattermill help pages, quoted above with the date we read them. Last reviewed 2026-11-12. We read them again by 2027-11-12. If one changes, this page changes or comes down.