!!!An important clarification!!!
Sometimes (2:22 to 2:24), the Stahanas (and other ships) render through the nebula poofs without any occlusion
This one is indeed a more general bug. It happens with EVERY ship that are cruisers or bigger. I have tried various different post 3.7.0 builds. The way this happens is VERY irregular. Usually it needs some action first; some projectiles flying in the space. For example during the mission "Proving Grounds" I can't reproduce this bug with Aquitaine in the beginning, but as soon as the attack starts, this bug also starts to happen. It doesn't happen
every time I face Aquitaine, but still too often. The basic sympton is that Aquitaine is 100 % visible for 1-2 seconds before FSO engine "remembers" to hide it behind nebula poofs. It's not game-breaking, but it takes away some immersion.
This also happens for Deimos corvettes and Shivan cruisers in the mission "Great Hunt".
I'm fairly certain that this is not an user-end issue. I have confirmed this behaviours with 2 different computers with modern hardware (like Geforce GTX 770) ja up-to-date drivers. I think my installation, settings and start parameters are also fine, since I have been able to complete dozens of campaigns last autumn. So this seems to be only a small rendering annoyance. My guess would be that FSO engine's "occlusion" mechanics are not currently handling well LOD changes of bigger ships, producing a delay of 1-2 seconds.