This looks very similar to a previous question, which is possibly related to bug 9495697, though it wasn't confirmed in that case. I can't share the bug details from MOS, but someone else has already done so.
As in that case, the symptoms you're experiencing on the base 11.2.0.1 release don't manifest for me on 11.2.0.3, or on SQL Fiddle, which is running 11.2.0.2.
If it is that bug then applying the 11.2.0.2 patch set should cure it, or a patch is available for just this issue; not sure if you need to raise a service request and get confirmation that the symptoms do match that specific bug before applying the patch though.