HomeKit randomly turns off guest access for smart lock

I have a Schlage Encode Plus smart lock on my door that responds fine to my phone and watch and to another person who’s identifies as a resident in the app. But I’ve got people with their own codes who have Guest status in the app, and their access keeps getting turned off. The sliders next to their names slide to the off position no matter what I do. I’ve removed and re-added the codes, I’ve reset the lock, removed and added it to HomeKit with the same result. They randomly get locked out, and I’m not able to grant them access to enter without giving them a key. I can’t manage access through the Schlage app because it’s integrated into HomeKit. I don’t know where the issue is. Any help would be appreciated.