I have noticed several graphics issues with the nacelles on the Comet Skin.
Will post pictures later today but here is description, I purchased the Comet Skin after S4 went live so I don't know if these existed beforehand.
Looking at the rear of the ship when flying in sector space or in system the right hand nacelle does not leave a trail, left one is fine.
When warping out of system the right hand nacelle does not display the warping effect, no glowing effect is present, the left hand one is fine and when you warp out you can also see a separate warp effect off to the left of the ship in space.
The buzzard collector on the right hand nacelle also does not look the same as the left one, it looks to have a different texture applied to it, it also has parts sticking out of the sides of the nacelle on both sides.
It looks like the wrong buzzard model was used as a guess.
I have changed the nacelles to one of the standard Recon Sci vessel ones and the issues are fixed, it is the same on Holodeck and Tribble.