The frustrating part is DashWare does not tell you there is an error. It just has a greyed out bar on the Synchronization page so you can't "seek" through the data and sync with the video. So there have probably been a number of people that have struggled through this issue and if it was their first attempt at overlaying in DashWare probably didn't think ti worked at all.
I have been editing the data to change the start of the data from 50:00.0 to 0:00.0 for example and then apply it to the rest of the cells in that column so that the session ends before I hit 59:59.9 (none of my sessions are over an hour so far). However, in my latest session this did not work for some reason. I'll see if I can troubleshoot it and will post back if I can fix it.
Harry, who do you think the problem lies with (HLT or DashWare)? I have not tried contacting DashWare at this point.
I have also attached the CSV of the session I am having an issue with. EDIT: Had to trim it because max file size is 256 kb
Here is a screeshot of a session that had this issue:

And what DashWare shows in the Sync tab (notice no GPS track outline, greyed out seek bar and no option to Sync to Video in bottom left):
