I want bring precision about this "bug". It's majoritary with the PAINT TOOL of plan build. With the simple toe tool, it's almost ok but sometimes this bug apear.
So. Thanks for your reply. I had test this mod (AdvancedTerrainModifiers) and the dev fonction OPPTERRAIN (maybe incorectly) but that's can't solve the problem. I think it's an mix of my few mods (I share list of them) and certainly due by all my contruction because my field is very full.
For the moment, I glitch with the simple hoe tool. It's not the best way but that's do the job... ;)