After an entire month of usage, it failed to open with any codes I've successfully used previously.  Luckily, I had my phone to unlock.  After several tries of removing/resetting procedure, I was able to get it working again.  A little annoyance, but let's hope it's a one time bug and not a repeat for when I really need it. Batteries were fine, but perhaps the recent temperature drop to 37 degrees might have been a factor.  This keypad is located inside my garage, so I imagine an optimal condition for its operation.