[engolling]

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So it might get stuck, if you reboot your WeatherDuino, but not the WeeWx machine and so on.
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This is one of the worst conditions that can happen, not only by an intentional reboot, but  also due to a power failure. Depending on the weather software used, this condition always cause some troubles, because during the WeatherDuino initialization there is no USB communication (this is intentional, and avoids even bigger problems). This matter was already discussed long time ago in several old topics, and it can be avoided.

That's right and the WeatherDuino behaves pretty fine in this case - better say nothing than false things. Also CumulusMX behaves great - I never got a bad conditions using those two.
I just wondering why I got those issue with WeeWx - but I might have been in combination with the Date-Time, I can not reproduce any more.

But in principle the direction should be clear and the solution easy... The weather station does not say anything as long it can not be sure that there is valid data. The software does not store anything and retries as long as it gets valid data from the weather station in the end. 

Nevertheless Zdenek's solution is preferable  . 
I got already the stuff for a small battery based on Li-Ion cells - I will build it... probably in 2019.

Regards,
engolling