Invisible blocking thing not allowing me to place stuff on it

I am making a map, and I can’t put any tiles on the top row for one specific map. Is this a bug? I’m using Tiled 1.6.

Hmm, at first glance I’m not sure what could be causing this. Could you possibly provide your files, either here or in a private message, so I could have a look at what’s happening here?

my map: test_collision_on_tile.tmx (1.3 KB)
my tileset !!!collision_tiles_TEST.tsx (1.8 KB) btw… it shows the stuff in the game, but it doesnt show in Tiled.