I must admit I was worried I would have to switch back to RC 3, but I don't like to be beaten, so I checked out the style editor, on the off chance I could figure out what was causing this odd behaviour. Now whether my solution was the only one, I have no idea, but it worked for me
As for checking out the migration from Rc3 to RC4, I did take a quick look at it, and was thinking maybe that script would solve the problem. However this is not an old scene, it is a brand new one, so definitely this particular preset, will need reworking for RC4. I've not had the time to check all the others yet, though I note that the guttering preset, states beta, in the Update Manager..
Talking of the guttering, it appears, at first glance, that in this beta version of the preset, you have solved the problem of brackets appearing on internal corners, which is excellent. I was meaning to ask about that a while ago, but since I don't see it happening with RC4, YET, there is no need.
So far RC4 is looking very impressive, though as yet I have been so busy I've not had enough time to really test it out.