Tonight was flying better than ever tracking my son on his bicycle.  Get inside to look at videos and his exciteable anticipation was replaced with boo. The icons/thumbnails were exclamation marks.

Do you have any screenshot or picture showing the error?

Sincere sorry for this unpleasant experience.

The video quality may be affected by the lighting, bitrate, flight environment, and flight distance. We respectfully suggest fly the aircraft in an open area on a sunny day with good light,  enable flight mode, and set the bitrate to 4 M and flight distance within 10 m to get better video quality.  

Meanwhile, as Jacksonnai suggested, please do feel free to shows us some screenshots or video showing your problem.

It was nearing sunset and dark outside... with the files not usable I had already deleted.  No worries.  Really enjoy the Tello.... for sure the gateway drone for getting hooked and wanting the bigger badder DJI options; I'm dreaming of a Mavic Pro Platinum