So recently I've installed a Huge Lot Sizes mod, but didn't turn out the way I like it, because flat roofs weren't displayed in Neighbourhood View nor in Live Mode for other Lots.

I uninstalled the mod completely, deleting the big Lot sizes, and the flat roofs in neighbourhood view were working again...but the Platforms I've place on top of the buildings are missing. It only happens for Lots I had changed with the mod installed.

Is there something I should install to fix this? or is this a sign of corruption? or is this caused by another unrelated mod? For example I'm using the Lot Lighting Fixes by LazyDuchess.

If you want the lot imposter to update, you have to make a change to the lot in build mode.

I tried that, didn't work. I even remade the platform roof from scratch.

Platforms not appearing on roofs is a vanilla bug, it has nothing to do with the large lot size mod and isn't a sign of corruption. Your game is working as designed.

How do I restore it then?

EDIT: So it turns out that adding a small fence on top of the platform renders it to not be shown in Lot imposter form after all...maybe it's due to the wallpaper not being changeable when the small fence on top is added?

I guess if I really want a fix, I'll just install the RPC features.