- No. I did not experience a similar problem but I am not using that kit.
- I do not like the direct powering of the RAK and so use a Waveshare D solar power manager and it allows you to make sure the power is always OK and reboot is ok if the battery is re-charged manually via USB. (The RAK runs for only about 5 days on one 18650 battery of 4500 mAh so you might be having this problem.) This was a topic in this thread Do RAK nodes always need manual reset after battery drain? - #10 by adingbatponder where I think what I was saying was misunderstood a for a while.
- I do not know if temperature was the cause of a problem. I ran my node in a box in the sun and it went to 55 C a couple of times and did not suffer … I was worried about this so did what is shown here (RAK Solar enclosure on hot days? Too hot inside? - #18 by ScoJa ) which is to put a layer of rubber spacers around the box and cover the whole thing in aluminium tape. This resulted in the same node box (details here Solar node for top of tall building ) not getting hotter than a few degrees above ambient temperature when the box was pointing north and shielded from the south by a metal mounting plate. I would therefore expect that you can prevent it getting so hot with simple measures but of course if the panel in part of the box then this is harder.
I am not sure BTW that a 4.0 V voltage on the battery means that the RAK is necessarily getting the right voltage. (I am no expert on this) … I would swap to a new fully charged battery and see if that changes something e.g. it re-starts. You could also just run it via USB power from a fat power bank to see if the thing also gives up after 5 days or just keeps going for much longer. Then it would be a battery draining issue and a re-start after drain issue (see item 2).
Good luck.