At www.fitfileviewer.com, I received many similar corrupted FIT files in the past weeks. I have not seen this type of corruption before, so I assume it is a bug in a recent software update on some devices. Typical for this corruption is:
- There is a file_id messages, but all values are invalid
- Many messages are missing, most notably the record messages, but also event, device_info etc.. Summary messages, like activity, session and lap are there.
- In several cases, but not always, many messages are duplicates, e.g. there are two identical activity messages, each lap and session appears twice.
FIT File Viewer can now fix these files, i.e. make it possible to import them in Garmin Connect, but of course it cannot restore the missing data.
I have seen this happening on FR 255, 955 and 965, and also in these threads:
