why there are so many failed videos?

I mass uploaded about 15 videos to my porn site at the same time, but failed about 4, the rest was pending for process etc...

2 days later I only see videos actual up and running. the rest has failed. 

if you open the database and go to ray_video_files i think it is you can set the failed ones back to pending then clear the cache in dolphin they will try and convert again.  if they fail again you will need to open ssh and watch the output of the cron job to see whats failing.