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 the 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