Thoughts:
Air can be free (a bubble at the top of a pipe/vessel), dissolved (in the water), or entrained (mixed with the water)
The amount of air that can be dissolved in water decreases with temperature and increases with pressure.
Heat the water and the dissolved air becomes entrained air. Entrained air will trip the flow sensor into an error state.
Entrained air doesn’t rise to the top of a vessel like free air. The only place entrained air becomes free air will be in radiators etc. Or in the (hot) coil of a hot water circuit when the heating cycle there stops. If there’s a coil with an appropriately placed auto-air vent this ought to (in time) purge the free air that un-dissolves as the water temperature rises, becomes entrained due to the water pumping around and around, then has an opportunity to rise up and out somewhere once the system flow stops.
Higher static fill pressures will mitigate / delay the onset of the symptoms.
If logic served I think a lower static fill pressure (and really cooking the water) will be more helpful for this purging process. (big district systems use vacuum degassers for this; these will eventually clear air pockets by dissolving them into the water then sucking that dissolved air out)
Then jacking up the static fill pressure.
Without an auto venting opportunity the only thing you can do is try to entrain the air and send it off out to the radiators (where it can become free air, and then rise to the top, and be let out before it gets cold again and becomes dissolved air) by alternating between heating and hot water mode with the system nice and red hot. Unlikely to be popular at this time of year!