That might be related to a memory leak I found with the picture editor. If I use the picture editor (opening, closing and saving) a lot on a layout with a lot of objects, eventually the interface tends gets messed up (indicating a memory leak, as it's the same thing that happened with another confirmed memory leak that was fixed). When I try to reproduce it though in a blank .cap, it doesn't happen, which is why I haven't reported it.
It's an annoying workaround, but I get around it by simply restarting construct after working with the picture editor a bit.