Thank you!
The movement is a bit confusing to get used to, but does have a logical reason behind it.
Basically, the raft only moves if there is a solid thing behind it, at the exact distance that is the current grid size, so if there is a wall in the tile behind the raft occupying the same location(even just a little bit), it moves at the current grid size. 
Another way to visualize it is to take the current tile or tiles the raft is in and move it to another tile or tiles (of the same grid size), if there is an overlap between the raft and another object, on that grid size, it acts as a wall and can never be occupied by the raft but can be used as a push off, if there is no overlap and the space is empty, the opposite is true. That's why you can hit a wall while visually not touching it, as if it did move another tile, the raft would overlap with something.
It could be made a bit clearer somehow but I'm not sure how to visually show that in a good way. 

Hopefully, my explanation made sense, thanks for giving it a go.

Thank you!
(4,2) Hint ->  Requires using the raft to offset the player's position onto the first 'stepping stone' (so they are aligned on it perfectly).
Alternatively, you can go down to the left, then exit back up and to the right from there, which leads to a similar thing.