I know if the terrain is 1024x1024 the 'patches' (for me) are usually around 64 each.
(Major Lag for me anyways, my computers a dinosaur)
Make sure that the size of the terrain patches are all possible for ^2 (so 8, 16, 32, 64, etc).
Might be why this is occurring, didn't bother to look at the source code yet XD
If it's performance issues.
Try implementing a LOD calculator (Level Of Detail).
I can't find a link for a explication of it so I'll put a brief description of it here
Basically it's a 'quality calculator'.Note
The further the camera is away from the terrain patch the lower 'patches inside patches' that will occur.
It makes a terrain patch that is far from you: render as 1 patch composed of 1 static geometry, instead of rendering as 1 patch composed of many static geometry's (High Texture Quality).
: If a LOD specialist comes along and finds this brief description wrong, this is from my own observations XD.
Hope it helps mate