I’ve noticed the terrain flattener is unuseable due to being really inaccurate.
If you try to flatten the terrain height it does not use the exact terrain height you started on and lowers everything in full voxels.
If you try to flatten lower terrain only to the current height and you clip inside of a mountain it creates a small air pocket and messes up the edges.
This prevents me from properly modifying the terrain.
The whole editor tool brush is bugged. I don’t think many people notice it though so roblox isn’t aware. I’ve been having all kinds of issues with brush tools not doing what they are supposed to do.
The fact that the automatic plane lock doesn’t work is ridicolous, the flatten tool is unusable 
Related to this bug report:
Thanks for the report. We’ll follow up when we have an update for you!
This needs to be fixed, the issue is very annoying.
When??? ᅠ ᅠ ᅠ ᅠ ᅠ ᅠ ᅠ ᅠ ᅠ ᅠ ᅠ ᅠ
Hi!
I just tried and it seems to work fine for me. May I ask for a place file you’re having issues with? The flatten tool also has options, like snapping to voxels and others. Make sure to turn off snapping if you don’t want snapping.
The problem with the Flatten tool for the past 7 months is that the tool has randomly started snapping every 4studs vertically, we can no longer be precise going between the 4stud levels, in other words the tool just creates steps in the terrain now and isn’t very useful.
Before, the flatten tool was a way to make precise slopes and to have the terrain at a very certain level within 0.1 which we no longer can.
And it’s not a problem with certain places, it happened for any place i made or joined, even on another account and another computer.
Hi! Can I ask for a place file to try to reproduce your issue?
you don’t need a place file, just open up a new file with terrain, this issue isn’t place dependent, don’t just use the tool from a distant and say it still works cause you can’t tell if you’re flattening at the height you actually chose… but it only flattens every 4 studs vertically which it shouldn’t do… the precision has vanished a year ago and has basically rendered the flatten tool useless.
I have this issue - when trying to flatten terrain it will subtract the terrain underneath the plane level instead of aligning with the plane I’ve selected. It is incredibly frustrating. Having to use grow / smooth instead with hours more work to try to fix the issue but still looks like a mess. It used to be a great tool