Doors, that are being unlocked with an electric strike, automatically lock themself again after a few seconds. This can be customised within a limit of 10 seconds. Please read these instructions to learn about how to change the unlock duration.
If you use Nuki alongside Klevio, you have two actions available in the Klevio App or Dashboard - lock and unlock. The doors won't lock themself after they've been unlocked, you have to perform that action by yourself through the App/Dashboard.