Already with the Nov. 2016 update it was not possible for me to make a shortcut for marker.
As well it is not possible with the Behringer X-Touch and also not with "M".
"Project -> Insert Marker" is somehow broken.
Also the "add track" dialog is randomly poping up.
I have already reported this weeks ago in this forum.
I think that only a few users have this problems. But I have this problem on several computers.