My Aug 2019 Karoq gave me the key battery low warning last week for the first time. Replaced the fob battery going by the book procedure with a new Kodak CR2025 dated 01/2028 and showing 3.3V off load. Didn't work. Tried again, numerous times and eventually it worked. When happy it was ok I did the spare key (actually I use them alternately) with another battery from the same pack. Didn't work; rinse and repeat; no joy. Went to supermarket, got some Energizer brand CR2025s and finally got the spare key to work ok. Next day: main key wouldn't work again. Replaced the new Kodak battery with another new Energizer and it worked. Why the hell are these fobs so fussy? And I wonder if at least some of the fob problems reported above could have been solved with a change of battery?
PS I hate the KESSY and disable it every time I leave the car, plus use Faraday pouches and a steering wheel lock (back to the 1970s). Means a button press is always needed to unlock the car. But AIUI the fobs will consume juice whether used or not, so I don't think my habit shortens battery life - not bad at two years anyway.