The current Orion TextView initialization is synchronous with some code that would need to become async. The current approach seems to cause random failures for us. See orion.textview.TextView._init().
We need to fix this problem upstream:
Async initialization has been added upstream but no "load" event. Also, there's no a DOMAttrModified event handler which slows down the parent document DOM operations. "Luckily" we are not affected because the SourceEditor re-wraps Orion into an iframe, so only that one is affected.
This is now entirely fixed upstream and the code has been integrated into our codebase, see bug 702331.