Strange flash bug

[Outcast]

I have noticed a strange bug in the flash runtime. I am making a line of sight event to make enemies track the player if they see him. I have stripped down this example to the bare minimum. There is a really strange problem though that occur in flash runtime. In regular runtime it works as expected, the line of sight line is only cut off if it breaks the line of sight by the block. In Flash however the line of sight is broken as soon as the player moves under the Y position of the block.

I did notice that this actually is possible to solve by having fine collision enabled on both object in flash, but I have no idea why that is needed in flash when it is not needed regulary, and it is really not good for performance if you need to have that on, especially not in flash where performance is a tricky thing to tackle on its own.

Do anyone know why this is happening and if there is another solution then to enable fine collision?

I have attached the example mfa.

Here is also a video demonstration of the problem for you who does not have the flash runtime to test on (only 300kb). On the right is the regular runtime, on left is flash runtime: https://dl.dropboxusercontent.com/u/...-18_012923.wmv