Here's a picture explaining what I mean:

http://i622.photobucket.com/albums/tt306/atibingler/ScreenShot21_zps69999f48.png

It's weird because some fire-sources cast shadows, and it looks weird when some do and some don't. So I'm turning to you guys, if you would know how to fix this issue? The only lighting mod I use is Realistic Lighting Overhaul. I thought such a comprehensive mod would fix things like these?

I've also looked at this mod, but haven't tried: http://skyrim.nexusmods.com/mods/27043//?

Would is fix it? It doesn't even say if it's compatible with RLO.

skyrim's shadows cause a huge performance hit + there is a maximum number of shadows, that can be displayed simultanously by the game engine.

in the creation kit, shadow casting can be turned on and off for each light individually. what you see has been done on purpose. many lighting overhaul mods do increase the number of shadows, but most try to keep it modest to save performance and avoid reaching the max shadow count.

this mod in particular (http://steamcommunity.com/sharedfiles/filedetails/?id=7914) is focussed on adding new shadows, keeping a vanilla look and feel while fixing some shadow bugs.