If you read the sequence I posted, I didn't really explain why it does each item.
First pressurize gallery and vent is to measure the pressure in the reservoir.
Run compressor and vent is a compressor function test (which is why it only pumps up to about 10 bar absolute and not the 17.7 bar threshold).
If the measurement in the first one was under the threshold it then starts the compressor and pumps the reservoir up. That's the second compressor run and third vent.
If the reservoir, pipework and center valve block is in good order, the second compressor run shouldn't happen each startup. It takes 2 or 3 measurement cycles to lose enough air to put the reservoir below the threshold.
The early software on the D3 didn't vent the reservoir after use and they found it was shortening the compressor life having it start up into a serious head pressure, which is why the revised software vents the gallery any time it's above 5 bar absolute and idle.
If you get the reservoir valve leak like I did, on a long trip it will slowly leak the reservoir into the gallery, the gallery will then exceed 5 bar and it'll vent. This will happen some 10 times and then the system will fault with the "too many cycles" error. On mine at that time it meant driving for more than ~2 hours 45 minutes without stopping (which I could never do with kids in the car).
