Unexplained occlusion

[MushyPeaBrain]

Did set change at lunch as usual. Felt fine on firing and bolused for my lunch. Just over an hour later vibe occlusion alarm goes off. First time on my new vibe pump. Primed and tried to bolus but alarmed straight off this time so pulled set. It looked perfect and only tiniest drop of blood at site. This is weird because always before with this alarm the cannula is kinked, it's a big bleeder or site gets sore and I can feel that too. No idea why this one alarmed. Any ideas anyone?

Have fired in a new set not far away so hoping this one is ok.