That is a really odd glitch. I'm not entirely sure how you could fix it.
You could try switching your Rendering System: Options>> Video>> Rendering System. The only thing I think would work is if you uninstall Feralheart, delete the Feralheart folder and re-download a new setup.
The thing is, I have a lot of addons, so that might be the problem. This glitch happens rarely, but when it happens it lags me more then playing MineCraft and Team Fortress 2 at the same time. I don't want to re-download Feralheart, because then I have to track down all the meshes, items, markings and mods that I have. Do you think there could be another way? If I didn't have all the downloads that I have, I probably would have already deleted and re-downloaded Feralheart.