Each file has a different file encoding even if they look alike. By default, the file encoding in Stock Sync is set to Auto.
It will use the lowest encoding. If you ever face a file encoding issue, please follow the steps below:
1. Identify your file encoding with http://www.abctool.info/encoding-detector/.
2. Once you have uploaded your file to that software, it will show your file encoding.
3. Navigate Feed Settings > Step 1 > File encoding and choose the from the list provided.
4. Rerun the feed