You can't have user interaction with a reactor, IIRC. If the block is part of the reactor, then that might make it error also, depends on how you have it coded. To edit an object that is the reason for the reactor, you might have to use a command ended reactor to actually edit the object, but if it's just a double click reactor then you might not have to. I would try coding it without user interaction, and see if it still crashes, if so, then you have to use the command ended way. That way you create a temp command ended reactor within the first reactor code.