Door open close single step problem

Guys,

got one Okuma Lb 25 lathe here doing strange things.
Although the sensors for "door opened" and "door closed" work perfectly ( they give right response in the OSP data when moving the door)...
one cannot run the single step mode for testing
programs with opened door like at any other Okuma lathe we run. I just can run single step with fully closed door OR...

Strange but true, if I manually manipulate the door opened sensor. Then
single step testing is possible ALTHOUGH the door is stil open and the OSP knows it is: both door closed AND door opened sensors give positives feedback simultaneously....WTF!?!

Is it a software error? Any parameter maybe set wrong?