I have a 910XT. It first started not uploading the latest activities. I managed to upload most of them by renaming the files on .../Sync/FIT_TYPE_4 folder to .fit and the using the import function on Garmin Connect. But the last three activities do not upload, and what I get from Garmin Express is that they are invalid files (see attached image). I can see the activities no problem on the device. These activities are important to analyze my progression towards my upcoming half ironman race. I already tryed removing the device from Garmin Express and uninstalling Garmin Express
Help appreciated
e