Suddenly cumulative water sensor is a negative value

Hi all!

Yesterday my Flukso (FLM03E) stopped pushing data on MQTT, something that happens to me every X months and then I need to reboot it to get everything working again.
Normally this doesn't have any side effects, but yesterday evening I rebooted the Flukso again and today I saw that the water sensor values were negative after the reboot and last night...

Data screen recording:

Someone that can explain this behaviour and how to fix the data?