My experience exactly - and when it refused to unlock with the fob, I did change the battery (and bought several long life spares).
Even pressing the key card over the lock symbol on the door pillar doesn't seem to work sometimes (and nor does the fob being pressed against the door pillar aswell).
I can walk last the card to open my garage and the car will unlock every time (even though I'm not using it) but when I'm out about I have to go through the charade of pressing the key fob in every orientation to get the car to unlock.
for the last two failed attempts I was able to open the tail gate and the rest of the car unlocked ??