Sluggo - This is all dependant on 'a certain point of view'.... but here's that 'possibility' about the recent anomaly you noted. Having now checked on this, it seems it is indeed only the biggest, foreground Stardestroyer in this shot below, that is progressively 'overshadowed' by the 'Executor'. The other 2 Stardestroyers in the 'distance' seem to be outside of the 'coverage' by the 'Executor's' hull, and are just already 'lit' in a steady 'half-shadow' like the biggest, foreground one is, at the start of the shot. (This particular shot shows the start, but the foreground Stardestroyer is eventually 'shadowed' all-over, before the shot changes) -
....the above shot changes to this one below, and I've always looked on the single 'distant' Stardestroyer in the shot below, as being the furthest back 'distant' one that was previously seen in the above shot....meaning that the furthest forward 'distant' Stardestroyer from the above shot, is now somewhere just out of the left of the frame of the shot below -
....and when the above shot then changes to this one below, that the furthest forward 'distant' Stardestroyer (seen in the top shot above), is now seen at this point, outside of the 'coverage' by the 'Executor's' hull -
....so that when the above shot changes to this one below, it now seems that the furthest forward 'distant' Stardestroyer is now 'hidden' on the other side of the 'Exector', with only the furthest back 'distant' one shown in the distance behind the nearest one to us, being 'passed-over' by the 'Executor' -
This is just my own preferred way of accounting for the layout of the shots above, and there are certainly some slight 'positioning issues' with this way of looking at this whole effects sequence.
However, I'm sure it could be argued that on the second shot from the top, that the single 'distant' Stardestroyer is the furthest forward one, and not the furthest back one....but that would make it seem as if we have gained yet another Stardestroyer in the overall 'Fleet' in the shot third from the top (which happened to be even further forward than the 2 seen in the top shot)....and that there is indeed now one of the top shot's 'distant' Stardestroyers missing in the bottom shot!
Unless Adywan decides differently, I'll look at it in the former way. What I'd quite like to see though, is a better 'positioning' of the 'passed-over' Stardestroyer in the bottom shot, in relation to the protruding 'centre detail' of the 'Executor's' underbelly hull, as is shown in the shot that precedes it (second from the bottom). Because in the bottom shot, it seems as if the 'passed-over' Stardestroyer is now further away from that part of the hull, compared to the shot that precedes it....
I hope you could all follow that, and my previous thoughts on it all. This now concludes all my 'existing Fleet shots' comments (about time some may say....), and I look forward to whatever Adywan chooses to amend, or not amend. In the meantime, ILM's effects are great, but their 'continuity' is a bit suspect at times....