This one, right?
My guess as to what happened, based on your other note in this thread:
The box is sold with the rail installed...keeps things together. The rail and the box are intentionally tight relative to each other to prevent the box from rattling on rail once installed. Off the bike, you've got a lot less leverage to overcome that friction...once installed, the frame becomes a pretty hefty object to pull against. So when removing the rail was difficult you assumed the button had something to do with it. But once the button clears the recess on the box...which is well before it travels far enough to pass beyond the hole in the rail and pop out the back...only friction between the rail and the box prevents the rail from moving. The button isn't involved anymore.
It's not a strong spring, so I'll grant you it's physically easy to push things beyond their functional limits.
ETA:fixed typo
Carl Matson
My guess as to what happened, based on your other note in this thread:
The box is sold with the rail installed...keeps things together. The rail and the box are intentionally tight relative to each other to prevent the box from rattling on rail once installed. Off the bike, you've got a lot less leverage to overcome that friction...once installed, the frame becomes a pretty hefty object to pull against. So when removing the rail was difficult you assumed the button had something to do with it. But once the button clears the recess on the box...which is well before it travels far enough to pass beyond the hole in the rail and pop out the back...only friction between the rail and the box prevents the rail from moving. The button isn't involved anymore.
It's not a strong spring, so I'll grant you it's physically easy to push things beyond their functional limits.
ETA:fixed typo
Carl Matson