@Solla-topee Thanks a lot for the reply and the link that explains the wake-up trigger.  I didn't expect that PIR is used not only for night, but also for day time. That gives me even more concern: would it be reasonably reliable during sunny and hot days?

I am using person and motion detection, and the sensitivity was at 7 and 8 respectively. I have adjusted the wake-up sensitivity from 7 to 8 and will give it a try.

This evening I also noticed two things: 1) I got two notifications just 1 second apart, but actually there was only one clip. 2) I went out to dump a bag which should be within 1 minute. That recorded video shows only part of it: it did not capture that I walked out of the door and it did not capture my return. 

I believe it is a fundamental design issue: Because it uses PIR, and because it does not do continuous recording, it is bound to miss a second or two of the beginning of motion. It is very clear: the PIR takes a bit time to trigger the wake-up, then it starts recording, that's where things get missed out in the recording.

I think, if imaging processing (i.e. not using PIR) takes too much power that solar panel can't cope with, the only solution is to enable continuous recording. Users may choose the time period of recording and may use less frames or resolutions to save power. Don't forget, although it is called battery powered, it does provide an USB-C port so that users can do wired power supply - in this case power consumption is not an issue to these users.

While I do think continuous recording is doable, I have the feeling that C410 will never get it. The reason: I have noticed the market is dumping C410 (since I bought it, the price has dropped twice, each time around 20%). I guess it may soon disappear from the market.

BTW, I have noticed there is a very high sensitivity here: I was saying I went out to dump r-a-b-i-s-h, I got a warning so I have to remove that word.