2014 Boxster. Sometimes, seemingly randomly, one of the key fobs will not work to unlock the car, etc. I get right up to the car and push the unlock button, then the lock button, then unlock, etc. and nothing happens. So I get the other key and it works fine and off I go. Later, the first key will work fine. After a few days it will happen again, although it may be that the second fob won't work but the first one will. The message that the battery in the fob is low and needs to be replaced has never come up on the multi-function display. I just replaced the batteries in both fobs because that seemed to be the obvious thing to do. It did not help. They both still work intermittently. Any thoughts or suggestions are appreciated. Thanks.