hang when changing stack height

[Martin Koob]

I have a sub-stack that contains a player object and a few buttons.

One button has a script to change the size of the stack and the size  
of the player object which allows the user can go between full size  
or half size.

Sometimes when  the script gets to the command to change the height  
the Beach ball appears and revolution(2.9) hangs, freezing the mac.   
I have to use the power button to shut down and restart.

Sometimes changing the height with the property inspector will cause  
revolution to hang,

Any ideas why this is happening.

Martin