@R0j0hound - I believe I've come across the same problem...but it's while going down slanted platforms where I've adjusted the collision polygon. I thought perhaps it was that BRIEF tick of time where the character box is dropping from one pixel height down to another, but even increasing gravity to lessen the theoretical time in the air falling, pressing the jump key seemed to lock him to the platform...much like @AngeloFernandes noticed, it wasn't until the end of the platform did the character jump.
If I'm reading your Event sheet right, you're telling C2 to position the Y of the player at its last position before there was an overlap with the platform's collision polygon...correct?
Can you also explain to me the dummy --> pair=platforma.pair Event condition? I don't get what's going on there.
I'm seeking Narnia. Who wants to come with me! Aslan is on the move!