Door sensor with contact can't change to CLOSE

I got an issue with door sensor, it works fine when item type is string, when door open/close, I can see it on habpanel it’s status, but if I set it as CONTACT, it couldn’t change from OPEN to CLOSE, It only change from NULL/CLOSE to OPEN.

Please tell me why, in, it should suit with it.

I got error below

09:33:34.405 [WARN ] [] - given new state is NULL, couldn’t post update for ‘WDS_Backdoor_WinDoorSensor2’

Contact WDS_Backdoor_WinDoorSensor2		"Compuroom Back Door Sensor [%d]"							(GT_Terrace, gSensor) 									{ mqtt="<[mosquitto:xiaomi/magnet/backdoor/158d000112aa5e/status:state:default"}

I got it works, I read the doc one more time and found it have to be CLOSED for close status, I make a transform and it works now