I've been testing this bug with automatic card placing disabled, and found out something interesting:
When the bug occurs, it offers as "valid" placement targets all of both your and your enemy's monster and S/T zones (even if they're occupied), the opponent's blue scale zone, your field zone and some other miscellanious like graves. Depending on what you select, different things happen:
1-If you select a monster or S/T zone on either side of the field: If your S/T zone of the same row as the zone you selected is empty, the card will be activated and placed face-up on that zone, apparently for no effect. If said zone is occupied, the card will activate on your hand... and remain there. You can repeat that as many times as you like.
2-If you select your field zone or the other miscellaea: Nothing happens. Despite being marked as valid placement target, the game doesn't let you place it there.
3-If you select the opponent's blue scale zone: "Error occurred" window pops up and the duel stops. Shame, it'd been a fun bug if it let you place it there.