Sorry if this has been reported before, but I think I have found a significant bug in MMF2 Build 248 (Dev).
Please run the attached mfa file.
Frame 1 shows a normal example where clicking a box will destroy it.
Frame 2 shows the bug where clicking a box will destroy all boxes. The only difference is that I have decided to run a loop on that condition which does nothing important.
Update: I just ran some more tests and if you change the action of the box in frame 2 to "Make Invisble" or even "Set position" it still does the same for all boxes. Therefore this would appear to be a problem with object selection.