Tomtom runner 3 shows battery empty but it's not after weird upgrade

matalena Registered Users Posts: 12
Apprentice Traveler
edited January 24 in TomTom Sports
Yesterday before going out walking I docked my runner 3 to charge it and got a message about an update. I chose to go ahead but the the watch started charging and I didn't see any update installation (weird). I the used my watch and the also this morning. At the end of today's walk I got the empty battery screen when, from my experience, the watch should have been still more than half full! Now at home I plugged it in and in fact it's more than half full. What is the problem? How can I make sure it does not happen again?
If the suggestion is doing a reset, I never did it before and I would like to know what will I lose and possibly where to find instructions on how to do it. Thanks a lot!
Currently the software indicates version 1.7.64.