NB: "Thankfully" the tree ghosting bug which I reported yesterday is helping to show where the trees were before I cut them down. (ghosting bug: Link)
I have the shadow setting set to Ultra. The shadows don't flicker, staying visible permanently, at least until I walk closer to them and then they gradually disappear.
Shadows of cut down trees still visible
"Tree ghosting bug" which sometimes causes cut-down trees to be redrawn alternate frames, which helps to show the shadows are related to where the trees were.