1. The Welcome message says I only used the machine for 3 hours and 40 minutes last night, which is way off. The web app "Dreammapper" has 8 hours and 19 minutes, which is about right.
2. Oscar's Daily chart has a start time of 22:52 last night, and an end time of 7:14 this morning, which is accurate and reflects the 8+ hours that Dreammapper reported.
3. The "Session information" summary shows a first session of 1 hr 17 min, and a second session of 2 hrs 22 mins. This leaves out most of the night. I did disconnect once to go to the bathroom, and the second session accurately represents the time after that. What's unexplained is why the first session ends after a little over an hour.
4. The "event flags" graph shows the whole night, including the bathroom break at 4:52.
5. Most of the other graphs show a long gap, from 1:52 to 4:52. That gap does not correspond to Session Information gap, which begins earlier. The Flow Rate, Mask Pressure, Insp. Time, Exp. Time, and Time at Pressure graphs all appear to be gapless. I'm not sure about the AHI graph, which may just be zero for much of the night.
6. Oscar's Daily chart says my AHI was 8.72, which is probably true for those 3 hours and 40 minutes. Dreammaper, and the machine display itself, have my AHI at 10.5 (machine) or 10.6 (Dreammapper). I think Dreammapper always rounds up.
7. Dreammapper reports three CA events, but of course it doesn't show when they occurred. Oscar shows none, in either the summary data or the Event Flags graph.
8. I tried importing into Sleepyhead, and it looks the same.
9. Scanning back over weeks and months, I find gaps from time to time. The first one I can find is back in May, 2018. They become a bit more frequent in 2019 -- maybe every couple of weeks -- then more frequent in the last few months. Again, I haven't been looking at anything except Dreammapper and the machine readout itself for quite a while, so I've been oblivious to this.
I'd be inclined to think that the problem is that the machine is not properly writing data to the card. Windows shows no bad sectors on the card itself.
Does that sound right?