I've been watching episodes of seasons randomly, mostly 1, 2, 3 and 4 and I noticed that the openings either are, in 4x3 with some 16x9 scenes, 4x3 with blur on the sides or 16x9. I'm not sure what went wrong here but why didn't they use one opening for the entire series only?

After all, this is the remastered widescreen edition so this shouldn't have happened.