As I introduced the patch which caused it I confirm it's in gnome-settings-daemon. Now there was one thing definitely causing this bug and I fixed that, there is a possible second cause of the same kind of behaviour and it sounds plausible that this would occur during window changes.
Thanks for everyone that added detail to this bug, it'll help when I start fixing it :)
As I introduced the patch which caused it I confirm it's in gnome-settings- daemon. Now there was one thing definitely causing this bug and I fixed that, there is a possible second cause of the same kind of behaviour and it sounds plausible that this would occur during window changes.
Thanks for everyone that added detail to this bug, it'll help when I start fixing it :)