Are they Sprites?
If they are then, did you check the collision polygon in the Image Editor if the polygons are spreading across the width of the sprite?
Not covering the entire width of the sprite sometimes cause this, especially when the sprites are moving in platformer games or etc.
If you want to make sure that the player has more chance of not falling -- in the image editor --> Collision Polygons (left-bottom side of the image editor) --> right click one of the dots and select set to bounding box...
Yeap, the sprites are invisible perfect rectangles (I used the default). The main problem seems to come from the transitions between the platform boxes. For eg, a horizontal rectangle on the left and an adjacent diagonal rectangle to the right of it. I'm guessing I might need to align the corner pixels of the transition together but it's difficult to do so on a large scale so I'm curious how you guys handle uneven platform creation