"Patience is really necessary."
Translation:Sự kiên nhẫn thật sự cần thiết.
I suppose it's because it is taking "thật sự" as "really", rather than just "thật", so "sự" doesn't combine with "cần thiết". I can't hear the audio now, so I don't know if it is distinguishable in speech.
Another discussion thread mentions "thực sự" as an alternate to "thật sự" - are they interchangeable?