Hey there @MR_Production! Welcome back to the community! So this is actually the stamp applied to the base landscape. Go ahead and click the eye icon on the layer that said flat middle and you can see it easier.
Then go to to the base landscape layer and use the erase tool to erase it. Then reenable the visibility for your other layer and you may need to adjust your terrain there as well. After that, you won’t have anymore worries!
