There is one known issue around button press, which will be addressed in the next beta (4.3.7). Please report back once the beta is out if your problem is solved with it.
Your Smart Lock is connected perfectly fine (via Thread) since a few days. If you still have problems you might switch back to WIFI. Follow this instructions to do so: Smart Lock WiFi/Thread/MQTT connection troubleshooting / FAQ - #3 by Stefan_Reiterer