Electrical – Is it OK that the circuit breaker panel does not latch closed

The two branch circuit breakers will trip if the load on their protected circuit is greater than 32 amperes, and 25 amperes respectively. However, since the main breaker trips at 40 amperes. If both branch circuits are pulling a full load the branch circuit breakers will not trip, but the combination of the loads will trip the main breaker (32 + 25 = 57 > 40 as you have said).

It's a very common situation to have the branch circuit breakers total more than the main breaker, but this is almost never a problem since the circuits usually don't pull a full load. Remember, circuit breakers are there to protect the wires. They shut off the power if you are drawing enough power to damage the wire, so installing a larger main breaker is likely not an option (unless you contact your power company and have the service upgraded, which will include upgrading the feeder cable).

Contact your local power company, and speak to them about a service upgrade. Other than plugging less stuff in, or cycling loads, there is not much you can do yourself in this situation.

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:

1. there was too much current flowing
2. 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.