I did a quick flight last night from a starting position with just stairs and in the fs2crew / pbe mixed scenario I'm running the pre-flight events only from fs2crew as instructed (I think you even removed the button from pbe in the latest beta if I remember correctly).

Could you migrate over the code you added to pbe to keep the stairs connected to fs2crew? I was also using self loading cargo and the stairs kept disconnecting which stops the boarding of passengers. I know I can just open the door without stairs, but I opened the ground control section of pbe and used the stairs button from there, which connected and kept them there. When it was time to go though pbe disconnected the stairs and then a weird dance of opening/closing the doors happened between the two applications? Not sure, but it only stopped after I quite pbe manually. I restarted it for the actual pushback and it was fine again.

Correct, if FS2Crew FBW and PBE are running at the same time, the Pre Flight Events button will be hidden in PBE so users don't try to start the Pre Fight Events in PBE.

This is to ensure users start Pre Flight Events in FBW only.

I think in FBW we do have the stairs code, but I'll check.  If it's not in FBW, we'll add the stairs code to it for the next public beta.

Cheers,