Google Sheets' IMPORTDATA randomly converts number

We have a simple REST endpoint that returns a number as a string. The number is rounded to two decimals and has a point, like this: 2385.1Google Sheets then sometimes transforms this into 177418 or some other nonsensical value.The endpoint has Content-Type set to to test/csv but we've also tried text/plain with the same effect. Changing the format of the cell didn't fix the problem.Any ideas how we can get Google Sheets to represent the number consistently?