Your labels are incorrect. You’ve labelled every tile as being the same - the same red terrain on every edge and every corner. This means those 9 tiles are all the same as far as Tiled is concerned, which is why you’re getting random results.
The red terrain should be only on those corners and edges where the tile has the dark orange artwork (or the light orange, depending on which you want to paint with, but definitely not both).
You’ll need to label all the tiles before Tiled can correctly use them, by the way. Even if you label them correctly, just 9 tiles isn’t enough for this terrain and the tool may still give nonsense results.
You may also want to make a second terrain colour for the other parts, so that those can correctly transition to other tiles that should transition to them (like the pink+yellow terrain tiles on the right in your screenshot). Note, however, if you do this, you’ll no longer be able to paint these terrains onto an empty map since they don’t have transitions to empty anymore, you’ll need to fill the map with some base tiles first.