I am using Firefox and I can get it to work and sync with one video in the raceQs folder. The problem manifests if there is more than one video file in the folder. It seems to reject all videos then. Note that I have not tested this extensively – I have only tried with two videos (and with unknown GoPro time data). The two videos are not for the same race and they do not overlap, nor do they exceed the duration of the GPS data.