After brainstorm about how figure it out and workaround this issue, I decided to contribute here about this issue.
On Landed trigger is not working properly when you have diagonal walls above the player head.
If you try to jump near a corner where your player don't have any vertical space between his collision box and the solids or obstacles, he will jump, and when On Landing, it will not check On, because he didn't jumped, but his animations and etc did.
So, because he didn't jumped, and falls, the On Landed didn't checked and your player will can walk around with the "Jumping" sprites On.
Here a sample file:
I'm working on a workaround, and making the code better too, simplifying and isolating some code parts, commenting, etc, so, this sample is a WIP, but still helping to reproduce the problem.
Any question, please, pop me a message.
Thanks you =]