This is what happens:
1 - I add a bookmark (keyboard)
2 - I collapse the routine
3 - I try to remove the bookmark, using the keyboard when the cursor is on the single line visible, Sub name. Instead of remove the bookmark (toggle), it adds a second bookmark to End Sub. Next time I press Alt+b on the Sub (collapsed) name, this last bookmark is removed (in short: only on "End Sub" the toggle works).