I work with iPad (3) too.
Sometimes a vid gives an error, if I push it again they work.
Its ****ty u have those problems, I hope I will be spared.
Maybe one thing:
In the past i had big problems with vids, not only here, but fb, youtube, just everywhere.
Since i have made lots more space on my iPad (deleted lots of apps and cleaned junkfiles) it runs smootly.
Maybe thats your problem? Just checking