Found it, it was a <densityMapHeightTypes> from my pack witch was in conflict with your buckwheat (but no idea how) not the fault of your mod then ;) . I use a small script to increase the filltypes limit to 1024 in my pack so I was confident about this possibility. Maybe you should add such script if you plan to add more filltypes in your production mod ?
Anyway, in checking my logs I found something wrong with buckwheat: Error: Could not find motion path effect for settings (Class: 'CutterMotionPathEffect', numRows: 32, rowLength: 42, fruitType 'BUCKWHEAT', growthState '5')