A couple of quick things, don’t use Z-Wave lock with codes, it actually doesn’t work with any lock management app and is a legacy DTH. The one to use with your Kwikset is “Z-Wave Lock” or this “Enhanced Z-Wave Lock” device handler only.
I believe the issue you’re facing is a quirk of the 910 lock (and similar locks with limited keypads). Basically this lock uses shared buttons due to which it has limited number of “unique” codes which can be programmed. You can find more details the issue documented:
- here: [RELEASE] Rental Lock Automater - Airbnb, VRBO, HomeAway, TripAdvisor, Booking, Expedia
- and here: [RELEASE] Lock User Management (LUM)
Basically you’ve got another code in the lock which is conflicting with the code you’re trying to program due to lack of unique buttons on the keypad. After reading the articles above you should be able to figure out which of your codes are conflicting based on the keypad layout and there after you should be able to your codes using LUM and the stock device handler without any issues.