The designer indeed loads the data in the background (using a task on a dispatch queue) and first does the plugins etc. and then the type converters. It could be that takes longer than anticipated, the form is shown and then the project is loaded (on the foreground thread) and things aren't ready.
(speculation as I can't repro it, but it looks like that's the situation you're running into). I can queue the project load into the same dispatch queue but then it loads slower than it does now, which is abit silly. The thing is that the language stuff for the editor takes a lot of time (relatively) to load, so queueing the project load after all that is noticable slower when double clicking (you'll look at the designer, empty and have to wait for 1-2 seconds before something happens).
Switching the order, so it first does type converters and then the rest would already solve things I think, however in theory it still can go wrong if there are many dlls in the type converter folder which cause exceptions so that task is slow and the project is then already loading...
We've now set the project to load at startup as a part of the initialization process of the designer and it's loaded in the background after the data needed is loaded, so it'll always be done after things are loaded properly.
This works OK and should solve your problem. I'll post a hotfix shortly so you can try it out.
