As I see the title of my post has been modified, I must outline that this issue is only persistent on the QualityWings 787-8 (maybe other variants). My stairs work perfectly fine on other aircraft
I just merged your post in a similar post discussing the issue of stairs not raising, it wasn't entirely clear from your first post it only happened with QW787, but not other planes.
You said you configured the airplane to use L2, which means you disabled L1 ? If you do that, you must also set L2 as the "Preferred Exit", by clicking on the small star icon in the airplane config dialog. I just tried it editing the default config for the QW787-8 doing these steps:
- I set L1 to be "No Door at this position"
- I left L2 as it were, just making it the "Preferred Exit"
Both stairs ( L2 and L4 ) raise normally.