In studio, I’ll occasionally load a place and for some rare reason an asset or two won’t load (I’ve only seen it happen with unions, but that may be because a missing decal isn’t as noticeable as a missing wall). Studio does not try to re-download the assets, and I have to re-open the place for the problem to be resolved. I have Settings > Rendering > ReloadAssets enabled, but I’m pretty sure that’s only related to reloading assets of physical files on your computer when the files update.
I used to have a weird router that would block traffic on a lot of ports, and since ROBLOX uses whatever ports are available, assets would frequently be downloaded through ports that the router was messing with and I’d get the white/black diamond texture on texture assets or have mesh assets not show up. It never seemed like ROBLOX tried to re-download those assets that had failed.
If an asset download fails, the download should be attempted again at least once – this goes for both the client and studio.