Pincode Lock Errors

I have had a couple customers in the past week or so that have complained that when using the winmo pincode lock that after a day or so the phone no longer unlocks. It basically acts like the password is incorrect and just erases the passcode after trying to unlock. I have seen it happen on one device and a hard reset fixed it but not sure if it has happened again. Any of you guys experienced this or heard about it? Doesn't happen with the slide lock feature or any other lock utility.