KB5017267　の WPFの更新内容に
Addresses issues arising in TreeView (or ListBox/DataGrid with grouping enabled)
when changing the underlying collection(s) while also collapsing or expanding TreeView nodes.
Scrolling actions, especially "short" actions like LineUp or MouseWheelUp,
can result in poor outcomes: hangs, crashes, unexpected scrolling, gaps in the display, etc.

とある。この辺が関係してそう。