Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
It is possible that part of the software that does the uploading has become corrupted.
What error message (if any) do you get when the upload of the workout fails?
Then, if workouts *since* the problem workout, are still uploading to the computer just fine, you probably have a spontaneous corruption of one workout on your Garmin device, at a guess.
Does that sound reasonable to you?
I might also ask, how old is the Garmin device in question? and how much use has it seen?
(I regret that I am not able to offer Live Phone Call service at this time; However, your request is still open to other Experts in this category, and one of them may pick up on it at any time.)
I was a little late noticing your message.
It appears you are not satisfied with my work so far.
I have Opted Out, opening the case to other Experts in this category. I hope another person's work will suit you better.
Thank you for following the process so far.