I didn't get to use the machine all night (I forgot it was just that much noisier than the PB330 & lost out on the negotiations with my wife to let me use it), but, I did spend some time trialling a few different things.
1) YES I was able to get it to trigger its alarm after using it for a while then coming back and reactivating it.
While I was doing these tests I had a pressure guage fitted so I could see what was happening (was the machine still trying to deliver the correct pressure).
It seems it was. What triggered the alarm seemed to be the change in breathing, it seemed to happen when I did a relaxed & slow breathing out soon after turning the blower back on. What the alarm is for is that the machine thinks an Apnea is occuring (the machine considers the user is not breathing). The Apnea alarm (1st setting after risetime) can be set to 0 (off) or 10, or 20 or 30 seconds.
The pressure guage showed everything was quite normal. So my answer to this problem ! - just turn off the apnea alarm off (set it to 0) or if you want it on for any reason set it to 30 secs
Perhaps you accidentally turned it on - it sure isn't needed if as happened in my case, there was no apnea happening.
I hope this is the answer you needed.
PS I set the machine for the tests as follows ...
0) Mode Bipap S/T
1) ipap 14
2) epap 10
3) risetime 2 (6 was far to slow & really does reduce the ventilation)
4) Insp time 2.2s
Other than the alarm going off. It worked pretty well.