PornBox.com

I think everyone decides to buy a video after enjoying the scenes shown in the trailer! For some time now, several videos have shown a trailer with only one scene, and often the model doesn't even take off her clothes, but mainly there are trailers without any action. Often the preview of the video has more content than the trailer, the problem is that the preview does not allow us to watch in full screen, and its duration is a maximum of 10 seconds! You can not evaluate the videos only with what is available in these videos. This occurs mainly in the videos of the producers: Outside The Studio, Briana Banderas Studio, Shinaryen's Pure Pleasure, Queen Eugenia Studio, Stacy Bloom Studio, among others. I was surprised that the RA029 video with Barbie Sins showed practically nothing, and she is one of the models I like the most.
HAVE TO SHOW ACTION ON THE TRAILER !!!!!
Another thing that has been happening a lot is the error when you click to watch the trailer, stating that the video was not found or is not available, I don't know the exact message because I went to execute some that were with this error yesterday, but today they are available .

Now that Pornbox sell clips from a wide range of content providers, some don't provide trailers, so I think Pornbox just show the first 30 seconds of the scene. Not that it helps much. It must limit sales appeal. But we can't expect Pornbox staff to make trailers for sellers who don't provide their own.

IMO best to review the screenshots for an impression of what a whole scene is like. Trailers are sales tools, so they show you what they want to show.

What OP calls a "preview" is, I think, just a random display of screenshots.