What does the latch position of a circuit breaker mean?
If you're referring to the circuit breaker switch being in the middle after it's been tripped, that's just the "tripped" position. As far as I know it doesn't tell you anything about the reason.

You have arc fault breakers, which means the breaker was tripped because:


there was too much current flowing
there was an arc fault.


Based on the relatively low loads and intermittence you describe, I would guess it's an arc fault issue. Perhaps a faulty wiring connection. Maybe it's being jostled occasionally if someone walks nearby and causes just the right vibration or something. Or as Steven mentions in a comment below, a faulty switch could cause an arc fault.