There's still a few issues that have been bugging me for a long time
1. Open spaces in the Brush where it does not grant visibility to the rest of the brush
Ever placed a ward in the brush and not have it grant visibility of the area? It's probably in one of the spots within the brush where it's bugged.
2. Edges of the brush do not grant visibility into the brush even when invisible to those outside
There's a thin layer on the outside of (all?) areas of brush where you can be invisible to those outside, but still not see into the brush behind you. Very annoying for champs like Blitzcrank who sit at the edge for more range to grab people.
3. Breaks spells sometimes even when visibility of the enemy is maintained
Champs sometimes flash in and out of visibility even when a ward is in the brush (I think this might have something to do with issue 1)