I was able to reproduce your problem. Solution:
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×I just moved over all the way to the right edge of the screen and then quickly back up. This gets the roaches into position with one of them on the bottom right door, and not on that corner that is giving you trouble. Then you can arrange the other corners as necessary without disturbing the upper right hand corner. Just be careful and you can get that corner after the orbs are struck.
Game on,
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"
He who is certain he knows the ending of things when he is only beginning them is either extremely wise or extremely foolish; no matter which is true, he is certainly an
unhappy man, for he has put a knife in the heart of wonder."
-- Tad Williams