sometimes the Barrier bugs out and can let go though it (not the sky barrier).

MC:PE bug reporting has been suspended on the Mojira. Please report bugs related to MC:PE via one of the following:

Reddit: http://www.reddit.com/r/MCPE/comments/2asho8/09x_bug_reports_submit_issues_here_and_only_here/

Minecraft Forums: http://www.minecraftforum.net/forums/minecraft-pocket-edition/mcpe-recent-upcoming-pe-updates/1998290-mcpe-bug-tracking-thread

If you fly up to the barrier it lets you go on an invisible block. It's been a bug for a long time. (Not the sky barrier).