Sprites can pass through other 1px wide sprites?

I am trying to remake a game with a left and right playfield where there is a 1 pixel wide dividing wall that occasionally moves position. When the wall is set to 2 pixels wide the player sprites (using gridmovement) cannot pass through them but when set to 1 pixel wide they do pass. Is this related to a collision mask bug I have been reading about?

If gridmovement supported a halt movement I could workaround this issue. Other wise I could have a seperate, invisible and wider walls for each side, but I would need help grouping:

left player+its wall to only collide

right player+its wall to only collide

Thanks.

<img src="http://i45.tinypic.com/34fl3ti.gif">

10 points if you can guess the game

It's not a bug, the Grid movement with "player controlled" checks if the sprite can move in a particular direction by checking if the sprite overlaps any solid at it's destination. If no collision is detected the sprite will move without checking the in between positions for collisions.

I whipped up an example on how to overcome the problem using the "Manual" mode of the grid movement and checking 1 pixel away before movement:

http://dl.dropbox.com/u/5426011/examples/grid.cap

req 0.99.84

Wow. Thanks very much.