RTC stops running causing Urban to appear frozen

[peter-mount]

After several weeks of running flawlessly (after the previous issues) my Urban board mounted outside stopped logging data on Monday evening.

Yesterday I took it down to look at the logs and I noticed it stopped because the alarm was set to a time in the past, so it wouldn't have triggered for just under 24 hours from the last reading.

Looking further into it, the RTC was not running at all. If I forced it to do an NTP update it would update but the alarm was still being set in the past and when the urban rebooted the RTC time was back to it's original value.

As I've got the urban on a permanent 4.5v supply and I have a Mastodon bot needing it I temporarily "fixed" it by replacing the RTC timer with a more basic time.sleep() call which seems to be working but means the pico is running all the time and not in deep sleep.

I do have a second Urban board which I got as a spare & to test the issues with #119 but that one hasn't experienced any issues until this morning, but that issue seems to be the one in #119 and not this one which is new.