NG Riello sporadic lockout

Parallax34

Hello I've been trying to diagnose a intermittent lockout on my ~1.5 yo Riello 40 G200. We had our Buderus G115 oil boiler converted to NG.

The hydronic system handles heat and hot water so it runs, to some degree, all year long but the lockout condition has never occurred in the summer. It only seems to happen when its below ~30 degrees outside and always at the least convenient times.

Pressing the reset button always fires it right back up and it operates for days to months before recuring.

I took a video of the boiler to observe its behavior when the lockout occurs, its always on startup and the burner does not go through its prepurge, just straight to lockout.

The manual suggests this state occurs when: "The air pressure switch does not change over from normally closed to normally open contacts, This condition exists because there is insufficient air pressure in the combustion head."

We had the plumber who installed the unit out to look at it but it was not faulting when he was here and so it was basically just a $300 trip to poke the burner and say that it looked fine.

So what would cause insufficient air pressure in the combustion head? Can I try and diagnose the pressure switch?

Any suggestions are appreciated its really annoying to have a heating system that can spontaneously trip at any time!