I've been searching for Roller coaster lots on reputable sims websites and haven't found any, so I was linked to some on the exchange. They look very nice but under test dirty on the 3 pack cleaner. Question is could this be a false dirty, like how the Custom Worlds come back dirty in the cleaner but aren't really corrupt, or is this really corrupt? I downloaded 3 lots from the exchange with real nice roller coasters and the 3 pack cleaner says they're all dirty. Here's a link to the screenshot of said dirties... https://1drv.ms/i/s!AoMbWxK0JvgIiIYcNqgYVAjS5SODmA

I attempted to help myself learn this answer but I am still needing more reassurance... here is what I found that indicates maybe I should just install it...

"This issue seems to only occur if you use save as. Downloading to the game directly works as intended."

But, if I do that, I have no way to check the content for corruption and forfeit the opportunity because its already installed by the time i find out its truly corrupt. What would our experts advise?

Those are thumbnails, in .png format. For some reason CUSTARD reads them as corrupt. You can ignore that, or deselect them and then save the sim3pack without them. That's what I do for lots.

Ok, I went ahead and saved it without them then. Hopefully it'll still load fine.

How did you download the lots? If you use the save to folder it frequently seems to mess up the download but if you use the add to game and let the launcher download it, it doesn't install it just puts it in the download folder and you can check it before you actually install it and change it to a package file if you prefer to put them in game that way.