That sounds just like my issue, What appears to happen is if the button cell is not charged enough and not connected, regardless of how well the main battery is charged, the laptop will assume it is booting for the first time.
With me, if i attached the mains lead briefly, without switching it on, and then disconnected the mains and powered on immediately afterwards then it would boot. But left any reasonable time off the mains would be treated as a full memory check (long booting sequence)
Thats why in my example i held the button battery down when switching off and on again, i would assume its because the button cell hasn’t had a chance to charge.
That’s my assumption anyway.