People have been noting this bug here for months - just posting again to bump the issue.
GC consistently notes stopped time during activities when there were no stops. Including during races when we barely even slowed down. It's most visible in the "Splits" panel, where we can distinguish any real stops from the erroneous discrepancies. Typically it's in the range of zero to eight seconds per each mile split.
Is Garmin's coding team even working on this?
I'm now wondering - now that my 920XT stopped accumulating distance while continuing to record other data, twice during the Boston Marathon - and now that several people have reported that same issue with their 620s and 630s - whether the bug is actually in some code common to these watches, but somehow it's now happening for several minutes at a time, whereas in the past it's only been for a second or so at a time, so it isn't noticeable to the user during a run, and short enough that it's not visible in the track - wondering if perhaps the issue isn't with GC at all, but rather with the way the watches note whether they're moving or not.
Sure would like to have some response on this issue.