In Island_SE.tmx the tile indices 35 and 67 in tilesheet island_tilesheet_2.png (the wood boards at the entrance to the cave) are given the property:
<property name="Passable" type="string" value="T" />
Tile index 35 is used at (29, 18) and (30, 18) while 67 is at (29, 19) and (30, 19).
However...