Hey! I wonder if its just me, but since tuesday my new imported sequences have skipped pictures like there is some kind of procedure deleting pictures before publishing. The effect can be seen here:
(dont look at the date, my go pro 7 again hanged up and reset the clock :-/ )
So it clearly shows regular 1s timelapse from go pro on the lower sequence and then uploaded few days later analogical 1s timelapse with lost pictures.
That behavior is really disapointing if its mapillary new saving space algoritm because some important places can be skipped :-/
The lower sequence also has track direction errors…
The first place to check is your source data. Do you still have all the georeferenced images? Do they all have valid Mapillary tags and not duplicates? Did the GPS remain solidly locked during the clock reset? There are many software packages that allow overlaying of georeferenced images on a map.
The lack of direction data is due to import from Gopro 7. I need to normalize each seqence after it showed up on the map (no auto normalize option).
But it appears I made a false alarm. Now the missing shots in the sequences are showing up gradually, instead of all sequence showing up complete at once. So EOT 
Experienced similar with the Desktop Uploader v1.2.4 for win10, after four days parts of several uploaded sequences are still missing, so will be re-uploading this night - and keep an eye on any doubles …